Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
hieu van » hieu va, thien van, lieu va
cam thuc » am thuc, nam thuc, cam thu
thuc van » thuc vat, thuc dan, thuc va
van tuan » van quan, van ban, anh tuan
sach ty » sach y, sach tu, sach thu
ty sang » ty xang, ty hang, duy sang
sang ma » tang ma, nang ma, sang tao
van cam » van nam, van lam, van cau
ma hoi » mai hoi, xa hoi, ma hoa

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 ty sang ma hoi. hieu van cam thuc van tuan ((ki su) or (ky su)) triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ty sang ma hoi. hieu van cam thuc van tuan ((ki su) OR (ky su)) triet.
• Adding a wildcard symbol may retrieve word variants: thu sach ty sang ma hoi. hieu van cam thuc van tuan ((ki su) or (ky su)) triet*.