Tài liệu tham khảo WikiPedia: Tia_âm_cực http://www.crtsite.com/page3.html http://www.youtube.com/watch?v=Xt7ZWEDZ_GI https://books.google.com/books?id=7-caAAAAYAAJ&pg=... https://books.google.com/books?id=ypNDAAAAcAAJ&pg=...