【October·咨询】请大佬帮忙分析一下：第一个逗号后的but引导的句子里，that引导的是什么从句呢？还有就是最后的which，我已经知道是非限制性定语从句了。但是它代指的是哪一部分呢？谢谢大家！
Yoga is usually best learned from a yoga teacher or physical therapist, but yoga is simple enough that one can learn the basics from good books on the subject, which are plentiful.
Yoga is usually best learned from a yoga teacher or physical therapist, but yoga is simple enough that one can learn the basics from good books on the subject, which are plentiful.
