diff --git a/books/free-programming-books-langs.md b/books/free-programming-books-langs.md
index 4b984845..6e906e8a 100644
--- a/books/free-programming-books-langs.md
+++ b/books/free-programming-books-langs.md
@@ -1321,6 +1321,7 @@ That section got so big, we decided to split it into its own file, the [BY SUBJE
 
 * [Kotlin Notes for Professionals](https://goalkicker.com/KotlinBook/) - Compiled from StackOverflow documentation (PDF)
 * [Kotlin Official Documentation](https://kotlinlang.org/docs/reference/)
+* [Kotlin Quick Reference](https://kotlin-quick-reference.com) - Alvin Alexander (gitbook)
 * [Learning Kotlin](https://riptutorial.com/Download/kotlin.pdf) (PDF)