- http://www.netflixprize.com/assets/GrandPrize2009_BPC_BellKor.pdf
- https://docs.google.com/presentation/d/1YMPJGo62hRPDz1iXQK2fITJAFOJn6H3oPD5vsrMwA1c/edit#slide=id.g9ee6c821b_9_53
- https://code.facebook.com/posts/861999383875667/recommending-items-to-more-than-a-billion-people/
- http://infolab.stanford.edu/~ullman/mmds/ch9.pdf
- http://files.grouplens.org/papers/algorithmstouserexperience.pdf
- http://fastml.com/evaluating-recommender-systems/
- https://en.wikipedia.org/wiki/Non-negative_matrix_factorization
- https://en.wikipedia.org/wiki/Recommender_system
- https://github.com/zipfian/DSI_Lectures/blob/master/topicmodeling/isaac_laughlin/nmf_nature.pdf
- https://github.com/zipfian/DSI_Lectures/blob/master/topicmodeling/jack_bennetto/NMF.ipynb
- http://www.quuxlabs.com/blog/2010/09/matrix-factorization-a-simple-tutorial-and-implementation-in-python/
- http://www.columbia.edu/~jwp2128/Teaching/W4721/Spring2015/papers/ieeecomputer.pdf
- https://en.wikipedia.org/wiki/Root-mean-square_deviation
- https://en.wikipedia.org/wiki/Discounted_cumulative_gain
- https://en.wikipedia.org/wiki/Precision_and_recall
- https://www.microsoft.com/en-us/research/publication/evaluating-recommender-systems/?from=http%3A%2F%2Fresearch.microsoft.com%2Fpubs%2F115396%2Fevaluationmetrics.tr.pdf
- https://ai2-s2-pdfs.s3.amazonaws.com/0fcc/45600283abca12ea2f422e3fb2575f4c7fc0.pdf
- https://spark.apache.org/docs/latest/ml-collaborative-filtering.html
- https://spark.apache.org/docs/latest/api/python/pyspark.ml.html#pyspark.ml.recommendation.ALS
- https://stackoverflow.com/questions/37260902/tuning-parameters-for-implicit-pyspark-ml-als-matrix-factorization-model-through
- https://datascience.stackexchange.com/questions/14744/spark-als-recommending-for-new-users/14750
- https://stackoverflow.com/questions/36723429/how-can-i-handle-new-users-items-in-model-generated-by-spark-als-from-mllib
- https://www.ismll.uni-hildesheim.de/pub/pdfs/Rendle2008-Online_Updating_Regularized_Kernel_Matrix_Factorization_Models.pdf
- https://stackoverflow.com/questions/30509335/how-to-update-spark-matrixfactorizationmodel-for-als
- https://stackoverflow.com/questions/41537470/als-model-how-to-generate-full-u-vt-v
- https://stackoverflow.com/questions/41568974/als-model-predicted-full-u-vt-v-ratings-are-very-high
- https://pdfs.semanticscholar.org/4af3/aaa876c3ad48db4180dc3253ce33f6943a45.pdf