Jose Portilla, Scala and Spark for Bit Data & Machine Learning (Udemy course), Link
Scala Docs, Link
Tutorials Point: Learn Scala Programming, Link
Marius Eriksen. Effective Scala, Link
Rob Story, Python to Scala, Link
Alvin Alexander, Scala Cookbook, Link
Scala Collections, Link
Martin Odersky, Programming in Scala, 3rd Edition, Link