[1] Similarity Metrics:
https://en.wikipedia.org/wiki/Metric_(mathematics)
[2] Distance Metrics ipynb:
https://github.com/RaRe-Technologies/gensim/blob/develop/docs/notebooks/distance_metrics.ipynb
[3] Hellinger Distance:
https://en.wikipedia.org/wiki/Hellinger_distance
[4] KL- divergence:
https://en.wikipedia.org/wiki/Kullback%E2%80%93Leibler_divergence
[5] Jaccard:
https://en.wikipedia.org/wiki/Jaccard_index
[6] Gensim wikipedia example:
https://radimrehurek.com/topic_modeling_tutorial/3%20-%20Indexing%20and%20Retrieval.html
[7] Simserver:
https://pypi.org/project/simserver/#description
[8] Doc Similarity Server:
https://radimrehurek.com/gensim/simserver.html
[9] Gensim SimServer GitHub:
https://github.com/RaRe-Technologies/gensim-simserver
[10] textRank:
http://web.eecs.umich.edu/~mihalcea/papers/mihalcea.emnlp04.pdf
[11] Variations of the Similarity Function...