diff --git a/chapter01.tex b/chapter01.tex
index 49a0342..c6651d5 100644
--- a/chapter01.tex
+++ b/chapter01.tex
@@ -846,13 +846,13 @@ $\lfloor \log_2(123)+1 \rfloor = 7$.
 
 \subsubsection{IOI}
 
-The International Olympiad in Informatics (IOI) \cite{ioi}
+The International Olympiad in Informatics (IOI)
 is an annual programming contest for
 secondary school students.
 Each country is allowed to send a team of
 four students to the contest.
 There are usually about 300 participants
-from 80 countries \cite{iois}.
+from 80 countries.
 
 The IOI consists of two five-hour long contests.
 In both contests, the participants are asked to
@@ -862,7 +862,7 @@ each of which has an assigned score.
 Even if the contestants are divided into teams,
 they compete as individuals.
 
-The IOI syllabus \cite{ioiy} regulates the topics
+The IOI syllabus \cite{iois} regulates the topics
 that may appear in IOI tasks.
 This book covers almost all topics in the IOI syllabus.
 
@@ -879,11 +879,11 @@ such as the Croatian Open Competition in Informatics (COCI)
 and the USA Computing Olympiad (USACO).
 In addition,
 many problems from Polish contests
-are available online \cite{main}.
+are available online\footnote{Młodzieżowa Akademia Informatyczna (MAIN), \texttt{http://main.edu.pl/}}.
 
 \subsubsection{ICPC}
 
-The International Collegiate Programming Contest (ICPC) \cite{icpc}
+The International Collegiate Programming Contest (ICPC)
 is an annual programming contest for university students.
 Each team in the contest consists of three students,
 and unlike in the IOI, the students work together;
diff --git a/list.tex b/list.tex
index 5cc1e00..6cd1b06 100644
--- a/list.tex
+++ b/list.tex
@@ -116,20 +116,8 @@
   A method for the construction of minimum-redundancy codes.
   \emph{Proceedings of the IRE}, 40(9):1098--1101, 1952.
 
-\bibitem{icpc}
-  The ACM-ICPC International Collegiate Programming Contest,
-  \url{https://icpc.baylor.edu/}
-
-\bibitem{ioi}
-  International Olympiad in Informatics -- Official site,
-  \url{http://www.ioinformatics.org/}
-
 \bibitem{iois}
-  International Olympiad in Informatics -- Statistics,
-  \url{http://stats.ioinformatics.org/}
-
-\bibitem{ioiy}
-  MisoF's IOI Syllabus page,
+  The International Olympiad in Informatics Syllabus, available at
   \url{https://people.ksp.sk/~misof/ioi-syllabus/}
 
 \bibitem{kar87}
@@ -152,10 +140,6 @@
   An $O(n \log n)$ algorithm for finding all repetitions in a string.
   \emph{Journal of Algorithms}, 5(3):422--432, 1984.
 
-\bibitem{main}
-  Młodzieżowa Akademia Informatyczna (MAIN),
-  \url{http://main.edu.pl/en}
-
 \bibitem{pac13}
   J. Pachocki and J. Radoszweski.
   Where to use and how not to use polynomial string hashing.