diff --git a/free-science-books.md b/free-science-books.md
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@@ -14,6 +14,7 @@
 * [Basics of Algebra, Topology, and Differential Calculus](http://www.cis.upenn.edu/~jean/math-basics.pdf) (PDF)
 * [Book Of Proof (2013)](http://www.people.vcu.edu/~rhammack/BookOfProof) - Richard Hammack
 * [Calculus](https://ocw.mit.edu/ans7870/resources/Strang/Edited/Calculus/Calculus.pdf) - Gilbert Strang (PDF)
+* [Calculus Better Explained](https://betterexplained.com/calculus/) - Kalid Azad (online)
 * [Calculus Made Easy](http://www.gutenberg.org/ebooks/33283) - Silvanus P. Thompson (PDF)
 * [College Geometry](http://math.unideb.hu/media/vincze-csaba/collegegeom-main-1.pdf) - Csaba Vincze and László Kozma (PDF)
 * [Computational Geometry](http://web.mit.edu/hyperbook/Patrikalakis-Maekawa-Cho/)