Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
cau tren » cu tren, dau tren, ca tren
nang co » nang cao, nang doc, nang noi
su sach » so sach, vu sach
hieu ve » hieu va, hieu van
cuc ban » cua ban, cac ban, cuu ban
hanh di » hanh vi, hanh de, hang di
co hoi » co hoc, co loi
di cau » da cau, diem cau
ve cac » va cac, vien cac

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

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