http://www.luyenthithukhoa.vn/index.php/tai-lieu/luyen-thi-dai-hoc-cao-dang/720-10-bai-toan-trong-diem-tu-duy-giai-nhanh-hinh-hoc-phang-oxy
Bạn nói gì mình không hiểu.https://diendan.hocmai.vn/threads/tai-lieu-sach-ve-phuong-trinh-duong-tron-va-bai-tap-ve-phuong-trinh-duong-tron.610742/