Perhaps you should try some spelling variations:
van thiet » va thiet, dan thiet, can thiet
sach thi » sach thu, sach tai, sach thieu
te sach » toc sach
nang va » nang van, hang va, bang va
nang ma » tang ma, sang ma, nang cao
hieu va » lieu va, hieu qua
cac tuc » cac toc, cac tu, cac tac
va hanh » van hanh, va thanh, va danh
tuc va » thuc va, truc va, tuc xa

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

• Performing a fuzzy search may retrieve terms with similar spellings: te sach thi ((nang va) or (nang ma)) hoi. hieu va cac tuc va hanh vi van thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach thi ((nang va) OR (nang ma)) hoi. hieu va cac tuc va hanh vi van thiet.
• Adding a wildcard symbol may retrieve word variants: te sach thi ((nang va) or (nang ma)) hoi. hieu va cac tuc va hanh vi van thiet*.