See also the following links:

▎ENGLISH

Machine Learning for Recommender systems
▸ https://medium.com/recombee-blog/machine-learning-for-recommender-systems-part-1-algorithms-evaluation-and-cold-start-6f696683d0ed

A Guide to Building Hybrid Recommendation Systems for Beginners
▸ https://analyticsindiamag.com/a-guide-to-building-hybrid-recommendation-systems-for-beginners/

▎日 本 語

情報推薦システム入門 (ハイブリッド型の説明は p.49-53)
▸ https://www.slideshare.net/KentaOku/ss-50762836

推薦システムを作るために決定木に基づく
▸ https://www.codetd.com/ja/article/6498636