Fix some broken links

docs/source/authors.rst

@@ -33,4 +33,4 @@ Contributors
 - Chinmaya Nagpal (chinmaya1011@gmail.com) resolved some issues with the
   packaging.
 
-.. _nicolas thiery: http://nicolas.thiery.name/
+.. _nicolas thiery: https://nicolas.thiery.name/

docs/source/index.rst

@@ -21,7 +21,8 @@ presented, semigroups and monoids. The main algorithms implemented in
   is decidable (such as transformations, partial permutations, permutations,
   bipartitions, and matrices over a semiring);
 - Kambites' algorithm for solving the word problem in small overlap monoids
-  from `Small overlap monoids I: The word problem <Small overlap monoids I>`_,
+  from
+  `Small overlap monoids I: The word problem <https://doi.org/10.1016/j.jalgebra.2008.09.038>`_,
   and the algorithm from
   `An explicit algorithm for normal forms in small overlap monoids`_;
 - the `Knuth-Bendix algorithm`_ for finitely presented semigroups and monoids;
@@ -48,11 +49,10 @@ presented, semigroups and monoids. The main algorithms implemented in
   see also `The Todd-Coxeter algorithm for semigroups and monoids`_.
 
 `libsemigroups`_ is partly based on
-`Algorithms for computing finite semigroups <Froidure-Pin algorithm>`_,
+`Algorithms for computing finite semigroups <https://www.irif.fr/~jep/PDF/Rio.pdf>`_,
 `Expository Slides`_, and `Semigroupe 2.01`_ by `Jean-Eric Pin`_.
 
 .. _Froidure-Pin algorithm: https://www.irif.fr/~jep/PDF/Rio.pdf
-.. _Small overlap monoids I: https://doi.org/10.1016/j.jalgebra.2008.09.038
 .. _An explicit algorithm for normal forms in small overlap monoids: https://doi.org/10.1016/j.jalgebra.2023.04.019
 .. _Knuth-Bendix algorithm: https://en.wikipedia.org/wiki/Knuth%E2%80%93Bendix_completion_algorithm
 .. _Computing finite index congruences of finitely presented semigroups and monoids: https://arxiv.org/abs/2302.06295

docs/source/libsemigroups.bib

@@ -76,7 +76,7 @@ @article{Aho1975aa
   title      = {Efficient string matching: an aid to bibliographic search},
   volume     = {18},
   issn       = {0001-0782, 1557-7317},
-  url        = {https://dl.acm.org/doi/10.1145/360825.360855},
+  url        = {https://doi.org/10.1145/360825.360855},
   doi        = {10.1145/360825.360855},
   shorttitle = {Efficient string matching},
   abstract   = {This paper describes a simple, efficient algorithm to locate all occurrences of any of a finite number of keywords in a string of text. The algorithm consists of constructing a finite state pattern matching machine from the keywords and then using the pattern matching machine to process the text string in a single pass. Construction of the pattern matching machine takes time proportional to the sum of the lengths of the keywords. The number of state transitions made by the pattern matching machine in processing the text string is independent of the number of keywords. The algorithm has been used to improve the speed of a library bibliographic search program by a factor of 5 to 10.},
@@ -410,17 +410,15 @@ @article{Moore1897aa
 	year = 1897}
 
 @book{Sims1994aa,
-	address = {Cambridge,, England, New York},
 	author = {Sims, Charles C.},
-	date-added = {2019-10-23 12:55:38 +0100},
-	date-modified = {2019-10-23 12:55:38 +0100},
-	isbn = {0-521-43213-8},
+	collection = {Encyclopedia of Mathematics and its Applications},
+	place = {Cambridge},
 	publisher = {Cambridge University Press},
-	series = {Encyclopedia of mathematics and its applications},
-	title = {Computation with finitely presented groups},
-	url = {http://opac.inria.fr/record=b1082972},
+	series = {Encyclopedia of Mathematics and its Applications},
+	title = {Computation with Finitely Presented Groups},
+	url = {https://doi.org/10.1017/CBO9780511574702},
 	year = 1994,
-	bdsk-url-1 = {http://opac.inria.fr/record=b1082972}}
+}
 
 @book{Knuth2009aa,
 	author = {Knuth, Donald E.},