diff --git a/Bookshelf/Apostol/Chapter_1_07.tex b/Bookshelf/Apostol/Chapter_1_07.tex
index e798ebf..53555f5 100644
--- a/Bookshelf/Apostol/Chapter_1_07.tex
+++ b/Bookshelf/Apostol/Chapter_1_07.tex
@@ -1,9 +1,9 @@
 \documentclass{article}
-\usepackage{amsmath}
+
 \usepackage{graphicx}
-\usepackage{mathrsfs}
 
 \input{../../preamble}
+
 \graphicspath{{./images/}}
 
 \newcommand{\larea}[2]{\lean{../..}{Common/Real/Geometry/Area}{#1}{#2}}
@@ -11,16 +11,18 @@
 
 \begin{document}
 
+\header{Exercises 1.7}{Tom M. Apostol}
+
 The properties of area in this set of exercises are to be deduced from the
   axioms for area stated in the foregoing section.
 
-\section{Exercise 1}%
-\label{sec:exercise-1}
+\section*{Exercise 1}%
+\hyperlabel{sec:exercise-1}%
 
 Prove that each of the following sets is measurable and has zero area:
 
-\subsection{Exercise 1a}%
-\label{sub:exercise-1a}
+\subsection*{\proceeding{Exercise 1a}}%
+\hyperlabel{sub:exercise-1a}%
 
 A set consisting of a single point.
 
@@ -36,8 +38,8 @@ A set consisting of a single point.
 
 \end{proof}
 
-\subsection{Exercise 1b}%
-\label{sub:exercise-1b}
+\subsection*{\proceeding{Exercise 1b}}%
+\hyperlabel{sub:exercise-1b}%
 
 A set consisting of a finite number of points in a plane.
 
@@ -50,7 +52,7 @@ A set consisting of a finite number of points in a plane.
   \paragraph{Base Case}%
 
     Consider a set $S$ consisting of a single point in a plane.
-    By \eqref{sub:exercise-1a}, $S$ is measurable with area $0$.
+    By \nameref{sub:exercise-1a}, $S$ is measurable with area $0$.
     Thus $P(1)$ holds.
 
   \paragraph{Induction Step}%
@@ -62,7 +64,7 @@ A set consisting of a finite number of points in a plane.
     Denote the remaining set of points as $S_k$.
     By construction, $S_{k+1} = S_k \cup T$.
     By the induction hypothesis, $S_k$ is measurable with area $0$.
-    By \eqref{sub:exercise-1a}, $T$ is measurable with area $0$.
+    By \nameref{sub:exercise-1a}, $T$ is measurable with area $0$.
     By the \larea{Additive-Property}{Additive Property}, $S_k \cup T$ is
       measurable, $S_k \cap T$ is measurable, and
       \begin{align}
@@ -82,7 +84,7 @@ A set consisting of a finite number of points in a plane.
 
       $S_k \cap T \neq \emptyset$.
       Since $T$ consists of a single point, $S_k \cap T = T$.
-      By \eqref{sub:exercise-1a}, $a(S_k \cap T) = a(T) = 0$.
+      By \nameref{sub:exercise-1a}, $a(S_k \cap T) = a(T) = 0$.
 
     \vspace{8pt}
     \noindent
@@ -95,8 +97,8 @@ A set consisting of a finite number of points in a plane.
 
 \end{proof}
 
-\subsection{Exercise 1c}%
-\label{sub:exercise-1c}
+\subsection*{\proceeding{Exercise 1c}}%
+\hyperlabel{sub:exercise-1c}%
 
 The union of a finite collection of line segments in a plane.
 
@@ -158,8 +160,8 @@ The union of a finite collection of line segments in a plane.
 
 \end{proof}
 
-\section{Exercise 2}%
-\label{sec:exercise-2}
+\section*{\unverified{Exercise 2}}%
+\hyperlabel{sec:exercise-2}%
 
 Every right triangular region is measurable because it can be obtained as the
   intersection of two rectangles.
@@ -209,8 +211,8 @@ Prove that every triangular region is measurable and that its area is one half
 
 \end{proof}
 
-\section{Exercise 3}%
-\label{sec:exercise-3}
+\section*{\unverified{Exercise 3}}%
+\hyperlabel{sec:exercise-3}%
 
 Prove that every trapezoid and every parallelogram is measurable and derive the
   usual formulas for their areas.
@@ -232,7 +234,7 @@ Prove that every trapezoid and every parallelogram is measurable and derive the
     Then $S$ is the union of non-overlapping rectangle $R$ of width $b_1$ and
       height $h$ with right triangle $T$ of base $b_2 - b_1$ and height $h$.
     By \larea{Choice-of-Scale}{Choice of Scale}, $R$ is measurable.
-    By \eqref{sec:exercise-2}, $T$ is measurable.
+    By \nameref{sec:exercise-2}, $T$ is measurable.
     By the \larea{Additive-Property}{Additive Property}, $R \cup T$ and $R \cap T$
       are both measurable and
       \begin{align*}
@@ -241,7 +243,8 @@ Prove that every trapezoid and every parallelogram is measurable and derive the
           & = a(R) + a(T) - a(R \cap T) \\
           & = a(R) + a(T) & \text{by construction} \\
           & = b_1h + a(T) & \text{Choice of Scale} \\
-          & = b_1h + \frac{1}{2}(b_2 - b_1)h & \eqref{sec:exercise-2} \\
+          & = b_1h + \frac{1}{2}(b_2 - b_1)h
+            & \text{\nameref{sec:exercise-2}} \\
           & = \frac{b_1 + b_2}{2}h.
       \end{align*}
 
@@ -251,7 +254,7 @@ Prove that every trapezoid and every parallelogram is measurable and derive the
     Then $S$ is the union of non-overlapping triangle $T$ and right trapezoid $R$.
     Let $c$ denote the length of base $T$.
     Then $R$ has longer base edge of length $b_2 - c$.
-    By \eqref{sec:exercise-2}, $T$ is measurable.
+    By \nameref{sec:exercise-2}, $T$ is measurable.
     By Case 1, $R$ is measurable.
     By the \larea{Additive-Property}{Additive Property}, $R \cup T$ and $R \cap T$
       are both measurable and
@@ -259,7 +262,7 @@ Prove that every trapezoid and every parallelogram is measurable and derive the
         a(S)
           & = a(T) + a(R) - a(R \cap T) \\
           & = a(T) + a(R) & \text{by construction} \\
-          & = \frac{1}{2}ch + a(R) & \eqref{sec:exercise-2} \\
+          & = \frac{1}{2}ch + a(R) & \text{\nameref{sec:exercise-2}} \\
           & = \frac{1}{2}ch + \frac{b_1 + b_2 - c}{2}h & \text{Case 1} \\
           & = \frac{b_1 + b_2}{2}h.
       \end{align*}
@@ -291,9 +294,7 @@ Prove that every trapezoid and every parallelogram is measurable and derive the
     These cases are exhaustive and in agreement with one another.
     Thus $S$ is measurable and $$a(S) = \frac{b_1 + b_2}{2}h.$$
 
-  \vspace{4pt}
-  \hrule
-  \vspace{10pt}
+  \divider
 
   Let $P$ be a parallelogram with base $b$ and height $h$.
   Then $P$ is the union of non-overlapping triangle $T$ and right trapezoid $R$.
@@ -317,15 +318,15 @@ Prove that every trapezoid and every parallelogram is measurable and derive the
 
 \end{proof}
 
-\section{Exercise 4}%
-\label{sec:exercise-4}
+\section*{Exercise 4}%
+\hyperlabel{sec:exercise-4}%
 
 Let $P$ be a polygon whose vertices are lattice points.
 The area of $P$ is $I + \frac{1}{2}B - 1$, where $I$ denotes the number of
   lattice points inside the polygon and $B$ denotes the number on the boundary.
 
-\subsection{Exercise 4a}%
-\label{sub:exercise-4a}
+\subsection*{\unverified{Exercise 4a}}%
+\hyperlabel{sub:exercise-4a}%
 
 Prove that the formula is valid for rectangles with sides parallel to the
   coordinate axes.
@@ -353,8 +354,8 @@ Prove that the formula is valid for rectangles with sides parallel to the
 
 \end{proof}
 
-\subsection{Exercise 4b}%
-\label{sub:exercise-4b}
+\subsection*{\unverified{Exercise 4b}}%
+\hyperlabel{sub:exercise-4b}%
 
 Prove that the formula is valid for right triangles and parallelograms.
 
@@ -396,19 +397,19 @@ Prove that the formula is valid for right triangles and parallelograms.
           & \eqref{sub:exercise-4b-eq1} \\
         & = \frac{1}{2}\left[ I_R + \frac{1}{2}B_R - 1 \right] \\
         & = \frac{1}{2}\left[ (w - 1)(h - 1) + \frac{1}{2}(2(w + h)) - 1 \right]
-          & \eqref{sub:exercise-4a} \\
+          & \text{\nameref{sub:exercise-4a}} \\
         & = \frac{1}{2}\left[ (w - 1)(h - 1) + w + h - 1 \right] \\
         & = \frac{1}{2}\left[ wh - w - h + 1 + w + h - 1 \right] \\
         & = \frac{wh}{2}.
     \end{align*}
 
   We do not prove this formula is valid for parallelograms here.
-  Instead, refer to \eqref{sub:exercise-4c} below.
+  Instead, refer to \nameref{sub:exercise-4c} below.
 
 \end{proof}
 
-\subsection{Exercise 4c}%
-\label{sub:exercise-4c}
+\subsection*{\unverified{Exercise 4c}}%
+\hyperlabel{sub:exercise-4c}%
 
 Use induction on the number of edges to construct a proof for general polygons.
 
@@ -421,7 +422,7 @@ Use induction on the number of edges to construct a proof for general polygons.
   \paragraph{Base Case}%
 
     A $3$-polygon is a triangle.
-    By \eqref{sub:exercise-4b}, the lattice point area formula holds.
+    By \nameref{sub:exercise-4b}, the lattice point area formula holds.
     Thus $P(3)$ holds.
 
   \paragraph{Induction Step}%
@@ -473,8 +474,8 @@ Use induction on the number of edges to construct a proof for general polygons.
 
 \end{proof}
 
-\section{Exercise 5}%
-\label{sec:exercise-5}
+\section*{\unverified{Exercise 5}}%
+\hyperlabel{sec:exercise-5}%
 
 Prove that a triangle whose vertices are lattice points cannot be equilateral.
 
@@ -487,7 +488,7 @@ ways, using Exercises 2 and 4.]
   Let $T$ be an equilateral triangle whose vertices are lattice points.
   Assume each side of $T$ has length $a$.
   Then $T$ has height $h = (a\sqrt{3}) / 2$.
-  By \eqref{sec:exercise-2},
+  By \nameref{sec:exercise-2},
     \begin{equation}
       \label{sub:exercise-5-eq1}
       \tag{5.1}
@@ -495,7 +496,7 @@ ways, using Exercises 2 and 4.]
     \end{equation}
   Let $I$ and $B$ denote the number of interior and boundary lattice points of
     $T$ respectively.
-  By \eqref{sec:exercise-4},
+  By \nameref{sec:exercise-4},
     \begin{equation}
       \label{sub:exercise-5-eq2}
       \tag{5.2}
@@ -509,8 +510,8 @@ ways, using Exercises 2 and 4.]
 
 \end{proof}
 
-\section{Exercise 6}%
-\label{sec:exercise-6}
+\section*{\unverified{Exercise 6}}%
+\hyperlabel{sec:exercise-6}%
 
 Let $A = \{1, 2, 3, 4, 5\}$, and let $\mathscr{M}$ denote the class of all
   subsets of $A$.
diff --git a/Bookshelf/Apostol/Chapter_1_11.tex b/Bookshelf/Apostol/Chapter_1_11.tex
index 8dfd3e2..6fc243b 100644
--- a/Bookshelf/Apostol/Chapter_1_11.tex
+++ b/Bookshelf/Apostol/Chapter_1_11.tex
@@ -1,25 +1,24 @@
 \documentclass{article}
-\usepackage{amsmath}
-\usepackage[shortlabels]{enumitem}
-\usepackage{soul, xcolor}
 
 \input{../../preamble}
 
 \newcommand{\link}[1]{\lean{../..}
-  {Bookshelf/Apostol/Chapter\_1\_11}
-  {Apostol.Chapter\_1\_11.#1}
-  {Chapter\_1\_11.#1}
+  {Bookshelf/Apostol/Chapter\_1\_11} % Location
+  {Apostol.Chapter\_1\_11.#1} % Namespace
+  {Chapter\_1\_11.#1} % Presentation
 }
 
 \begin{document}
 
-\section{Exercise 4}%
-\label{sec:exercise-4}
+\header{Exercises 1.11}{Tom M. Apostol}
+
+\section*{Exercise 4}%
+\hyperlabel{sec:exercise-4}%
 
 Prove that the greatest-integer function has the properties indicated:
 
-\subsection{Exercise 4a}%
-\label{sub:exercise-4a}
+\subsection*{\proceeding{Exercise 4a}}%
+\hyperlabel{sub:exercise-4a}%
 
 $\floor{x + n} = \floor{x} + n$ for every integer $n$.
 
@@ -29,8 +28,8 @@ $\floor{x + n} = \floor{x} + n$ for every integer $n$.
 
 \end{proof}
 
-\subsection{Exercise 4b}%
-\label{sub:exercise-4b}
+\subsection*{\proceeding{Exercise 4b}}%
+\hyperlabel{sub:exercise-4b}%
 
 $\floor{-x} =
   \begin{cases}
@@ -49,8 +48,8 @@ $\floor{-x} =
 
 \end{proof}
 
-\subsection{Exercise 4c}%
-\label{sub:exercise-4c}
+\subsection*{\proceeding{Exercise 4c}}%
+\hyperlabel{sub:exercise-4c}%
 
 $\floor{x + y} = \floor{x} + \floor{y}$ or $\floor{x} + \floor{y} + 1$.
 
@@ -60,8 +59,8 @@ $\floor{x + y} = \floor{x} + \floor{y}$ or $\floor{x} + \floor{y} + 1$.
 
 \end{proof}
 
-\subsection{Exercise 4d}%
-\label{sub:exercise-4d}
+\subsection*{\proceeding{Exercise 4d}}%
+\hyperlabel{sub:exercise-4d}%
 
 $\floor{2x} = \floor{x} + \floor{x + \frac{1}{2}}.$
 
@@ -71,8 +70,8 @@ $\floor{2x} = \floor{x} + \floor{x + \frac{1}{2}}.$
 
 \end{proof}
 
-\subsection{Exercise 4e}%
-\label{sub:exercise-4e}
+\subsection*{\proceeding{Exercise 4e}}%
+\hyperlabel{sub:exercise-4e}%
 
 $\floor{3x} = \floor{x} + \floor{x + \frac{1}{3}} + \floor{x + \frac{2}{3}}.$
 
@@ -82,24 +81,20 @@ $\floor{3x} = \floor{x} + \floor{x + \frac{1}{3}} + \floor{x + \frac{2}{3}}.$
 
 \end{proof}
 
-\section{Exercise 5}%
-\label{sec:exercise-5}
+\section*{\proceeding{Exercise 5}}%
+\hyperlabel{sec:exercise-5}%
 
 The formulas in Exercises 4(d) and 4(e) suggest a generalization for
   $\floor{nx}$.
 State and prove such a generalization.
 
-\vspace{6pt}
-\noindent
-\hl{Note}: The stated generalization is known as "Hermite's Identity."
+\note{The stated generalization is known as "Hermite's Identity."}
 
 \begin{proof}
 
   \link{exercise\_5}
 
-  \vspace{10pt}
-  \hrule
-  \vspace{10pt}
+  \divider
 
   We prove that for all natural numbers $n$ and real numbers $x$, the following
     identity holds:
@@ -132,7 +127,7 @@ State and prove such a generalization.
           & = \floor{n(\floor{x} + r)} \nonumber \\
           & = \floor{n\floor{x} + nr} \nonumber \\
           & = \floor{n\floor{x}} + \floor{nr}. \nonumber
-            & \eqref{sub:exercise-4a} \\
+            & \text{\nameref{sub:exercise-4a}} \\
           & = \floor{n\floor{x}} + j \nonumber \\
           & = n\floor{x} + j. \label{sec:exercise-5-eq3}
       \end{align}
@@ -175,8 +170,8 @@ State and prove such a generalization.
 
 \end{proof}
 
-\section{Exercise 6}%
-\label{sec:exercise-6}
+\section*{\unverified{Exercise 6}}%
+\hyperlabel{sec:exercise-6}%
 
 Recall that a lattice point $(x, y)$ in the plane is one whose coordinates are
   integers.
@@ -199,15 +194,15 @@ Prove that the number of lattice points in $S$ is equal to the sum
 
 \end{proof}
 
-\section{Exercise 7}%
-\label{sec:exercise-7}
+\section*{Exercise 7}%
+\hyperlabel{sec:exercise-7}%
 
 If $a$ and $b$ are positive integers with no common factor, we have the formula
   $$\sum_{n=1}^{b-1} \floor{\frac{na}{b}} = \frac{(a - 1)(b - 1)}{2}.$$
 When $b = 1$, the sum on the left is understood to be $0$.
 
-\subsection{Exercise 7a}%
-\label{sub:exercise-7a}
+\subsection*{\unverified{Exercise 7a}}%
+\hyperlabel{sub:exercise-7a}%
 
 Derive this result by a geometric argument, counting lattice points in a right
   triangle.
@@ -218,8 +213,8 @@ Derive this result by a geometric argument, counting lattice points in a right
 
 \end{proof}
 
-\subsection{Exercise 7b}%
-\label{sub:exercise-7b}
+\subsection*{\proceeding{Exercise 7b}}%
+\hyperlabel{sub:exercise-7b}%
 
 Derive the result analytically as follows:
 By changing the index of summation, note that
@@ -232,8 +227,8 @@ Now apply Exercises 4(a) and (b) to the bracket on the right.
 
 \end{proof}
 
-\section{Exercise 8}%
-\label{sec:exercise-8}
+\section*{\unverified{Exercise 8}}%
+\hyperlabel{sec:exercise-8}%
 
 Let $S$ be a set of points on the real line.
 The \textit{characteristic function} of $S$ is, by definition, the function
diff --git a/Bookshelf/Apostol/Chapter_I_03.tex b/Bookshelf/Apostol/Chapter_I_03.tex
index 54f16d2..2f5a229 100644
--- a/Bookshelf/Apostol/Chapter_I_03.tex
+++ b/Bookshelf/Apostol/Chapter_I_03.tex
@@ -1,5 +1,4 @@
 \documentclass{article}
-\usepackage[shortlabels]{enumitem}
 
 \input{../../preamble}
 
@@ -11,8 +10,10 @@
 
 \begin{document}
 
-\section*{Theorem I.27}%
-\label{sec:theorem-i.27}
+\header{A Set of Axioms for the Real-Number System}{Tom M. Apostol}
+
+\section*{\proceeding{Theorem I.27}}%
+\hyperlabel{sec:theorem-i.27}%
 
 Every nonempty set $S$ that is bounded below has a greatest lower bound; that
 is, there is a real number $L$ such that $L = \inf{S}$.
@@ -23,8 +24,8 @@ is, there is a real number $L$ such that $L = \inf{S}$.
 
 \end{proof}
 
-\section*{Theorem I.29}%
-\label{sec:theorem-i.29}
+\section*{\proceeding{Theorem I.29}}%
+\hyperlabel{sec:theorem-i.29}
 
 For every real $x$ there exists a positive integer $n$ such that $n > x$.
 
@@ -34,20 +35,22 @@ For every real $x$ there exists a positive integer $n$ such that $n > x$.
 
 \end{proof}
 
-\section*{Theorem I.30 (Archimedean Property of the Reals)}%
-\label{sec:theorem-i.30}
+\section*{\proceeding{Theorem I.30}}%
+\hyperlabel{sec:theorem-i.30}%
 
 If $x > 0$ and if $y$ is an arbitrary real number, there exists a positive
 integer $n$ such that $nx > y$.
 
+\note{This is known as the "Archimedean Property of the Reals."}
+
 \begin{proof}
 
   \link{exists\_pnat\_mul\_self\_geq\_of\_pos}
 
 \end{proof}
 
-\section*{Theorem I.31}%
-\label{sec:theorem-i.31}
+\section*{\proceeding{Theorem I.31}}%
+\hyperlabel{sec:theorem-i.31}%
 
 If three real numbers $a$, $x$, and $y$ satisfy the inequalities
 $$a \leq x \leq a + \frac{y}{n}$$
@@ -59,8 +62,8 @@ for every integer $n \geq 1$, then $x = a$.
 
 \end{proof}
 
-\section*{Theorem I.32}%
-\label{sec:theorem-i.32}
+\section*{\proceeding{Theorem I.32}}%
+\hyperlabel{sec:theorem-i.32}%
 
 Let $h$ be a given positive number and let $S$ be a set of real numbers.
 \begin{enumerate}[(a)]
@@ -81,8 +84,8 @@ Let $h$ be a given positive number and let $S$ be a set of real numbers.
 
 \end{proof}
 
-\section*{Theorem I.33 (Additive Property)}%
-\label{sec:theorem-i.33}
+\section*{\proceeding{Theorem I.33}}%
+\hyperlabel{sec:theorem-i.33}%
 
 Given nonempty subsets $A$ and $B$ of $\mathbb{R}$, let $C$ denote the set
 $$C = \{a + b : a \in A, b \in B\}.$$
@@ -94,6 +97,8 @@ $$C = \{a + b : a \in A, b \in B\}.$$
     $$\inf{C} = \inf{A} + \inf{B}.$$
 \end{enumerate}
 
+\note{This is known as the "Additive Property."}
+
 \begin{proof}
 
   \  % Force space prior to *Proof.*
@@ -105,8 +110,8 @@ $$C = \{a + b : a \in A, b \in B\}.$$
 
 \end{proof}
 
-\section*{Theorem I.34}%
-\label{sec:theorem-i.34}
+\section*{\proceeding{Theorem I.34}}%
+\hyperlabel{sec:theorem-i.34}%
 
 Given two nonempty subsets $S$ and $T$ of $\mathbb{R}$ such that
 $$s \leq t$$
diff --git a/Bookshelf/Enderton/Chapter0.tex b/Bookshelf/Enderton/Chapter0.tex
index d25cd7b..d9a2caf 100644
--- a/Bookshelf/Enderton/Chapter0.tex
+++ b/Bookshelf/Enderton/Chapter0.tex
@@ -3,17 +3,20 @@
 \input{../../preamble}
 
 \newcommand{\link}[1]{\lean{../..}
-  {Bookshelf/Enderton/Chapter0}
-  {Enderton.Chapter0.#1}
-  {Chapter0.#1}
+  {Bookshelf/Enderton/Chapter0} % Location
+  {Enderton.Chapter0.#1} % Namespace
+  {Chapter0.#1} % Presentation
 }
 
 \begin{document}
 
-\section*{Lemma 0A}%
-\label{sec:lemma-0a}
+\header{Useful Facts About Sets}{Herbert B. Enderton}
 
-Assume that $\langle x_1, \ldots, x_m \rangle = \langle y_1, \ldots, y_m, \ldots, y_{m+k} \rangle$.
+\section{\proceeding{Lemma 0A}}%
+\hyperlabel{sec:lemma-0a}%
+
+Assume that $\langle x_1, \ldots, x_m \rangle =
+  \langle y_1, \ldots, y_m, \ldots, y_{m+k} \rangle$.
 Then $x_1 = \langle y_1, \ldots, y_{k+1} \rangle$.
 
 \begin{proof}
diff --git a/Common/Real/Sequence/Arithmetic.tex b/Common/Real/Sequence/Arithmetic.tex
index f183efc..190d1f8 100644
--- a/Common/Real/Sequence/Arithmetic.tex
+++ b/Common/Real/Sequence/Arithmetic.tex
@@ -3,15 +3,15 @@
 \input{../../../preamble}
 
 \newcommand{\link}[1]{\lean{../../..}
-  {Common/Real/Sequence/Arithmetic}
-  {Real.Arithmetic.#1}
-  {Real.Arithmetic.#1}
+  {Common/Real/Sequence/Arithmetic} % Location
+  {Real.Arithmetic.#1} % Namespace
+  {Real.Arithmetic.#1} % Presentation
 }
 
 \begin{document}
 
-\section*{Sum of Arithmetic Series}%
-\label{sec:sum-arithmetic-series}
+\section{\proceeding{Sum of Arithmetic Series}}%
+\hyperlabel{sec:sum-arithmetic-series}%
 
 Let $(a_i)_{i \geq 0}$ be an arithmetic sequence with common difference $d$.
 Then for some $n \in \mathbb{N}$,
diff --git a/Common/Real/Sequence/Geometric.tex b/Common/Real/Sequence/Geometric.tex
index b048ef4..56b1a63 100644
--- a/Common/Real/Sequence/Geometric.tex
+++ b/Common/Real/Sequence/Geometric.tex
@@ -3,15 +3,15 @@
 \input{../../../preamble}
 
 \newcommand{\link}[1]{\lean{../../..}
-  {Common/Real/Sequence/Geometric}
-  {Real.Geometric.#1}
-  {Real.Geometric.#1}
+  {Common/Real/Sequence/Geometric} % Location
+  {Real.Geometric.#1} % Namespace
+  {Real.Geometric.#1} % Presentation
 }
 
 \begin{document}
 
-\section*{Sum of Geometric Series}%
-\label{sec:sum-geometric-series}
+\section{\proceeding{Sum of Geometric Series}}%
+\hyperlabel{sec:sum-geometric-series}%
 
 Let $(a_i)_{i \geq 0}$ be a geometric sequence with common ratio $r \neq 1$.
 Then for some $n \in \mathbb{N}$,
diff --git a/preamble.tex b/preamble.tex
index 855a02f..9aecbe7 100644
--- a/preamble.tex
+++ b/preamble.tex
@@ -1,15 +1,66 @@
-\usepackage{amsfonts, amsthm}
+\usepackage{amsfonts, amsmath, amsthm}
+\usepackage[shortlabels]{enumitem}
+\usepackage{environ}
+\usepackage{fancybox}
+\usepackage{fontawesome5}
 \usepackage{hyperref}
+\usepackage{mathrsfs}
+\usepackage{soul, xcolor}
 
-\newtheorem{theorem}{Theorem}
-\newtheorem{xtheoreminner}{Theorem}
-\newenvironment{xtheorem}[1]{%
-  \renewcommand\thextheoreminner{#1}%
-  \xtheoreminner
-}{\endxtheoreminner}
+% ========================================
+% Linking
+% ========================================
 
 \hypersetup{colorlinks=true, urlcolor=blue}
 
+% The first argument refers to a relative path upward from a current file to
+% the root of the workspace (i.e. where this `preamble.tex` file is located).
+% #1 - Path to root
+% #2 - Location
+% #3 - Namespace
+% #4 - Presentation
+\newcommand{\lean}[4]{\href{#1/#2.html\##3}{#4}}
+\newcommand{\hyperlabel}[1]{%
+  \label{#1}%
+  \hypertarget{#1}{}}
+
+% ========================================
+% Environments
+% ========================================
+
+\newcommand{\divider}{%
+  \vspace{10pt}
+  \hrule
+  \vspace{10pt}}
+\newcommand{\header}[2]{%
+  \title{#1}
+  \author{#2}
+  \date{}
+  \maketitle}
+\newcommand{\note}[1]{%
+  \begin{center}
+    \doublebox{
+      \begin{minipage}{0.95\textwidth}
+      \vspace{2pt}
+      \hl{Note}: #1
+      \vspace{2pt}
+      \end{minipage}}
+  \end{center}}
+
+% Status of a proof. A statement/theorem is verified if both a LaTeX proof
+% and a corresponding Lean proof has been written. If a Lean proof is in
+% progress, it's in a "proceeding" state. Otherwise it is unverified.
+\DeclareRobustCommand{\verified}[1]{%
+  \texorpdfstring{\color{teal}#1\ \faCheckCircle}{#1}}
+\DeclareRobustCommand{\proceeding}[1]{%
+  \texorpdfstring{\color{magenta}#1\ \faSpinner}{#1}}
+\DeclareRobustCommand{\unverified}[1]{%
+  \texorpdfstring{\color{red}#1\ \faExclamationCircle}{#1}}
+
+% ========================================
+% Math
+% ========================================
+
 \newcommand{\abs}[1]{\left|#1\right|}
 \newcommand{\ceil}[1]{\left\lceil#1\right\rceil}
 \newcommand{\floor}[1]{\left\lfloor#1\right\rfloor}
@@ -17,6 +68,3 @@
 \newcommand{\ico}[2]{\left[#1, #2\right)}
 \newcommand{\ioc}[2]{\left(#1, #2\right]}
 \newcommand{\ioo}[2]{\left(#1, #2\right)}
-% The first argument refers to a relative path upward from a current file to
-% the root of the workspace (i.e. where this `preamble.tex` file is located).
-\newcommand{\lean}[4]{\href{#1/#2.html\##3}{#4}}