Fixed links in documentation

src/rsprocess/bisimilarity/bisimilarity_kanellakis_smolka.rs

@@ -1,6 +1,6 @@
 //! Bisimilarity by Kanellakis and Smolka from The algorithmics of bisimilarity
 //! by Luca Aceto, Anna Ingolfsdottir and Jirí Srba; pages 105 to 110
-//! https://doi.org/10.1017/CBO9780511792588.004
+//! <https://doi.org/10.1017/CBO9780511792588.004>
 
 use std::collections::{BTreeSet, HashMap, HashSet};
 

src/rsprocess/bisimilarity/bisimilarity_paige_tarkan.rs

@@ -1,6 +1,6 @@
 //! Bisimilarity by Paige and Tarjan from Three Partition Refinement Algorithms
 //! by Robert Paige L., Robert Endre Tarjan; pages 977 to 983
-//! https://doi.org/10.1137/0216062
+//! <https://doi.org/10.1137/0216062>
 
 use std::cell::RefCell;
 use std::collections::hash_map::Entry;