Perhaps you should try some spelling variations:
nang cau » nang cao, hang cau, nang dau
hieu van » hieu va, thien van, lieu va
cua viet » ca viet, hoa viet, cua vat
su sach » so sach, vu sach
sach ty » sach y, sach tu, sach thu
ty nang » ky nang, ty xang, ty hang
cac duc » cac du, cao duc, cac nuoc
cac dac » cac dan, cac dai, cac bac
va hanh » van hanh, va thanh, va danh
vi cua » vai cua, di cua

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 ty nang cau hoi. hieu van ((cac duc) or (cac dac)) va hanh vi cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ty nang cau hoi. hieu van ((cac duc) OR (cac dac)) va hanh vi cua viet.
• Adding a wildcard symbol may retrieve word variants: su sach ty nang cau hoi. hieu van ((cac duc) or (cac dac)) va hanh vi cua viet*.