Russian-Notes Reference: The New Penguin Russian Course 俄语历史语法概论 - 杨隽 俄语常用词快速记忆 - 阎国栋 https://www.russianlessons.net http://www.study-languages-online.com/russian-grammar.html http://openrussian.org https://github.com/leoarnold/russian-grammar-tables