Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
thi hang » thi hanh, thi nang, thi hong
hieu va » lieu va
cam tuc » cam xuc, cam tu, nam thuc
va hanh » van hanh, va thanh, va danh
va hoi » xa hoi, va hoc, va hoa
tuc va » thuc va, truc va, tuc xa
vi va » vi van, vai va, vu va
thiet » thieu

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) OR (toc sach)) thi hang va hoi. ((hieu va) or (hieu qua)) cam tuc va hanh vi va thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (toc sach)) thi hang va hoi. ((hieu va) OR (hieu qua)) cam tuc va hanh vi va thiet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((te sach) OR (toc sach)) thi hang va hoi. ((hieu va) or (hieu qua)) cam tuc va hanh vi va thiet".
• Adding a wildcard symbol may retrieve word variants: ((te sach) OR (toc sach)) thi hang va hoi. ((hieu va) or (hieu qua)) cam tuc va hanh vi va thiet*.