Stuff from the internet on evaluating RS

Hello recommender engine enthusiasts,

Just completely accidentally came across this great answer from Xavier on quora on the topic of evaluating the recommender systems and the importance of A/B testing. Here is the link https://www.quora.com/How-do-you-measure-and-evaluate-the-quality-of-recommendation-engines

Inside his response he mentions other very interesting articles on his paper and on talks of other people, recommend reading it.