Introduction to Commercial Systems
:: Amazon recommender systems: https://www.cs.umd.edu/~samir/498/Amazon-Recommendations.pdf
:: Netflix recommender systems: https://medium.com/netflix-techblog/netflix-recommendations-beyond-the-5-stars-part-1-55838468f429

Tutorial on Building a Recommender
:: Building a movie recommender: http://blog.manugarri.com/a-short-introduction-to-recommendation-systems/
:: Building a music recommender: https://medium.com/towards-data-science/genre-essentials-building-an-album-recommender-system-c89c308d16f0

Evaluation of Recommender Systems
:: https://medium.com/recombee-blog/evaluating-recommender-systems-choosing-the-best-one-for-your-business-c688ab781a35

List of Recommender Systems in Use
:: https://github.com/grahamjenson/list_of_recommender_systems