Perhaps you should try some spelling variations:
hoach dat » hoach xay, hoc dat, hoach va
thu sach » tu sach, thuat sach, thuoc sach
nang mai » nang ma, nang tai, lang mai
hieu van » hieu va, thien van, hieu ve
va thanh » gia thanh, ban thanh, va tinh
thanh vi » hanh vi, thanh va, thanh ve
sach ky » sac ky, sach y, sach ty
mai hoi » mai khoi, dai hoi, lai hoi
hac dat » hoc dat, tac dat, nhac dan
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: thu sach ky nang mai hoi. ((hieu van) or (lieu va)) ((hac dat) or (hoach dat)) va thanh vi cua vat~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ky nang mai hoi. ((hieu van) OR (lieu va)) ((hac dat) OR (hoach dat)) va thanh vi cua vat.
• Adding a wildcard symbol may retrieve word variants: thu sach ky nang mai hoi. ((hieu van) or (lieu va)) ((hac dat) or (hoach dat)) va thanh vi cua vat*.