diff --git a/chapter19.tex b/chapter19.tex
index 1163cec..d000a7e 100644
--- a/chapter19.tex
+++ b/chapter19.tex
@@ -398,8 +398,9 @@ so we have successfully constructed an Eulerian circuit.
 
 \index{Hamiltonian path}
 
-A \key{Hamiltonian path}\footnote{
-W. R. Hamilton (1805--1865) was an Irish mathematician.} is a path
+A \key{Hamiltonian path}
+%\footnote{W. R. Hamilton (1805--1865) was an Irish mathematician.}
+is a path
 that visits each node in the graph exactly once.
 For example, the graph
 \begin{center}
@@ -485,12 +486,12 @@ Also stronger results have been achieved:
 \begin{itemize}
 \item
 \index{Dirac's theorem}
-\key{Dirac's theorem} \cite{dir52}:
+\key{Dirac's theorem}: %\cite{dir52}
 If the degree of each node is at least $n/2$,
 the graph contains a Hamiltonian path.
 \item
 \index{Ore's theorem}
-\key{Ore's theorem} \cite{ore60}:
+\key{Ore's theorem}: %\cite{ore60}
 If the sum of degrees of each non-adjacent pair of nodes
 is at least $n$,
 the graph contains a Hamiltonian path.
@@ -529,7 +530,9 @@ It is possible to implement this solution in $O(2^n n^2)$ time.
 
 \index{De Bruijn sequence}
 
-A \key{De Bruijn sequence}\footnote{N. G. de Bruijn (1918--2012) was a Dutch mathematician.} is a string that contains
+A \key{De Bruijn sequence}
+%\footnote{N. G. de Bruijn (1918--2012) was a Dutch mathematician.}
+is a string that contains
 every string of length $n$
 exactly once as a substring, for a fixed
 alphabet of $k$ characters.
diff --git a/chapter20.tex b/chapter20.tex
index 9ca3eb0..1e7a8d0 100644
--- a/chapter20.tex
+++ b/chapter20.tex
@@ -930,7 +930,7 @@ The maximum flow of this graph is as follows:
 \index{Hall's theorem}
 \index{perfect matching}
 
-\key{Hall's theorem} \cite{hal35} can be used to find out
+\key{Hall's theorem} can be used to find out
 whether a bipartite graph has a matching
 that contains all left or right nodes.
 If the number of left and right nodes is the same,
@@ -1020,7 +1020,7 @@ has at least one endpoint in the set.
 In a general graph, finding a minimum node cover
 is a NP-hard problem.
 However, if the graph is bipartite,
-\key{Kőnig's theorem} \cite{kon31} tells us that
+\key{Kőnig's theorem} tells us that
 the size of a minimum node cover
 and the size of a maximum matching are always equal.
 Thus, we can calculate the size of a minimum node cover
@@ -1409,7 +1409,7 @@ An \key{antichain} is a set of nodes of a graph
 such that there is no path
 from any node to another node
 using the edges of the graph.
-\key{Dilworth's theorem} \cite{dil50} states that
+\key{Dilworth's theorem} states that
 in a directed acyclic graph, the size of
 a minimum general path cover
 equals the size of a maximum antichain.
diff --git a/list.tex b/list.tex
index b7f34d7..be0c952 100644
--- a/list.tex
+++ b/list.tex
@@ -59,15 +59,15 @@
   A note on two problems in connexion with graphs.
   \emph{Numerische Mathematik}, 1(1):269--271, 1959.
 
-\bibitem{dil50}
-  R. P. Dilworth.
-  A decomposition theorem for partially ordered sets.
-  \emph{Annals of Mathematics}, 51(1):161--166, 1950.
+% \bibitem{dil50}
+%   R. P. Dilworth.
+%   A decomposition theorem for partially ordered sets.
+%   \emph{Annals of Mathematics}, 51(1):161--166, 1950.
 
-\bibitem{dir52}
-  G. A. Dirac.
-  Some theorems on abstract graphs.
-  \emph{Proceedings of the London Mathematical Society}, 3(1):69--81, 1952.
+% \bibitem{dir52}
+%   G. A. Dirac.
+%   Some theorems on abstract graphs.
+%   \emph{Proceedings of the London Mathematical Society}, 3(1):69--81, 1952.
 
 \bibitem{edm65}
   J. Edmonds.
@@ -147,10 +147,10 @@
   Computer Science and Computational Biology},
   Cambridge University Press, 1997.
 
-\bibitem{hal35}
-  P. Hall.
-  On representatives of subsets.
-  \emph{Journal London Mathematical Society} 10(1):26--30, 1935.
+% \bibitem{hal35}
+%   P. Hall.
+%   On representatives of subsets.
+%   \emph{Journal London Mathematical Society} 10(1):26--30, 1935.
 
   On representatives of subsets. J. London Math. Soc, 10(1), 26-30.
 
@@ -211,10 +211,10 @@
   D. E. Knuth.
   \emph{The Art of Computer Programming. Volume 3: Sorting and Searching}, Addison–Wesley, 1998 (2nd edition).
 
-\bibitem{kon31}
-  D. Kőnig.
-  Gráfok és mátrixok.
-  \emph{Matematikai és Fizikai Lapok}, 38(1):116--119, 1931.
+% \bibitem{kon31}
+%   D. Kőnig.
+%   Gráfok és mátrixok.
+%   \emph{Matematikai és Fizikai Lapok}, 38(1):116--119, 1931.
 
 \bibitem{kru56}
   J. B. Kruskal.
@@ -231,10 +231,10 @@
   An $O(n \log n)$ algorithm for finding all repetitions in a string.
   \emph{Journal of Algorithms}, 5(3):422--432, 1984.
 
-\bibitem{ore60}
-  Ø. Ore.
-  Note on Hamilton circuits.
-  \emph{The American Mathematical Monthly}, 67(1):55, 1960.
+% \bibitem{ore60}
+%   Ø. Ore.
+%   Note on Hamilton circuits.
+%   \emph{The American Mathematical Monthly}, 67(1):55, 1960.
 
 \bibitem{pac13}
   J. Pachocki and J. Radoszweski.