So, three good examples of applying self-determination theory, to make a gamified site, even when using the standard PBL elements, feel more intrinsically motivating. If you're interested in more on self-determination theory, two good books to recommend. One is a book called Drive by Daniel Pink, and this is a kind of business popularization of self-determination theory. He recounts the history of the work by Deci and Ryan. And then shows how this kind of approach can be applied in business, and gives some great examples of companies, that are using these kinds intrinsic motivators for great success. Really well written book, if you want to. Understand how this, these concepts apply in business. It's not about gamification per se, but it's very relevant to the discussions that we have in this course. The second one is by Richard Ryan, and a co-author, Scott Rigby and it is specifically applying self-dermination theory to video games. It's called, Glued to Games. And it shows some of their research on, specifically, how video games can activate these three motivators of self-determination theory. So, ideally, every gamification implementation, should be based on some attempt to engage these aspects of intrinsic motivation, which self-determination theory outlines