http://mccormickml.com/2018/06/15/applying-word2vec-to-recommenders-and-advertising/
https://static.googleusercontent.com/media/research.google.com/en//pubs/archive/45530.pdf
https://arxiv.org/pdf/1606.07792.pdf
https://www.cse.iitk.ac.in/users/nsrivast/HCC/Recommender_systems_handbook.pdf Netflix challenge solution at high level: https://datajobs.com/data-science-repo/Recommender-Systems-[Netflix].pdf
https://towardsdatascience.com/prototyping-a-recommender-system-step-by-step-part-1-knn-item-based-collaborative-filtering-637969614ea https://towardsdatascience.com/prototyping-a-recommender-system-step-by-step-part-2-alternating-least-square-als-matrix-4a76c58714a1