Perhaps you should try some spelling variations:
tham thuc » pham thuc, tam thuc, thai thuc
nham thuc » nhan thuc, nam thuc, nham thu
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
hieu va » lieu va, hieu qua
ky tang » ky nang, ky dang, kho tang
huu tre » huu tri, cuu tre, huu them
ma hoi » mai hoi, xa hoi, me hoi
va dan » ca dan, va dao, va dau
dan va » doan va, dan ca, ban va
va huu » vu huu

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach ky tang ((ma hoi) or (ma hoa)). hieu va ((nham thuc) or (tham thuc)) va dan va huu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky tang ((ma hoi) OR (ma hoa)). hieu va ((nham thuc) OR (tham thuc)) va dan va huu tre.
• Adding a wildcard symbol may retrieve word variants: tu sach ky tang ((ma hoi) or (ma hoa)). hieu va ((nham thuc) or (tham thuc)) va dan va huu tre*.