Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
nang cau » nang cao, hang cau, nang dau
cau tren » cu tren, dau tren, ca tren
su sach » so sach, vu sach
hieu ve » hieu va, hieu van
cac tuc » cac toc, cac tu, cac tac
tuc cua » thuc cua, tac cua, luc cua
cua dan » cua dang, cua ban, ca dan
ve cac » va cac, vien cac
ca cau » cua cau, cac cau, can cau

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: ((su sach) or (((te sach) or (toc sach)))) ky nang cau hoi. hieu ve cac tuc cua dan ca cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((su sach) OR (((te sach) OR (toc sach)))) ky nang cau hoi. hieu ve cac tuc cua dan ca cau tren.
• Adding a wildcard symbol may retrieve word variants: ((su sach) or (((te sach) or (toc sach)))) ky nang cau hoi. hieu ve cac tuc cua dan ca cau tren*.