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 ### Abstract Algebra
 - *Fraleigh, John B.* A First Course in Abstract Algebra.
 - **Paper - In Arabic -** *AlYasry, A.* The Concept of Equivalence and its Classes in Mathematics. [[Online](https://drive.google.com/file/d/1EvN7xxAk787kpHTbI_jBkjKgLD_ymexs/view)]
+- *Lang, S.* Undergraduate Algebra. [[Online](https://link.springer.com/book/10.1007/0-387-27475-8)]
 
 ### Number Theory
 - *Serre, J. P.* A Course in Arithmetic[^jps]. [[Online](https://link.springer.com/book/10.1007/978-1-4684-9884-4)]