RT goldengrape: springer限免! 好多书是epub的, 比PDF舒服多了!
https://link.springer.com/search?facet-content-type=%22Book%22&package=mat-covid19_textbooks&facet-language=%22En%22&sortOrder=newestFirst&showAll=true
但如果真正阅读英文有困难的时候, 可以使用我写的生词注释程序: https://github.com/goldengrape/explanation_words_in_ebooks
