Perhaps you should try some spelling variations:
tham thuc » nham thuc, pham thuc, tam thuc
cau theo » cau thi, cau tao
hanh tai » thanh tai, hang tai, han tai
hieu va » lieu va, hieu qua
tai cau » tai cac, tai cao
va hanh » van hanh, va thanh, va danh
thuc va » thuc vat, thuc dan, thuc day
tu sach » thu sach, su sach, te sach
sach ty » sach y, sach tu, sach thu
hieu ve » hieu van
tang ma » mang may, tang van
mang xa » lang xa, mang may, dang xay

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 ty ((mang xa) or (tang ma)) hoi. ((hieu ve) or (hieu va)) tham thuc va hanh tai cau theo~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ty ((mang xa) OR (tang ma)) hoi. ((hieu ve) OR (hieu va)) tham thuc va hanh tai cau theo.
• Adding a wildcard symbol may retrieve word variants: tu sach ty ((mang xa) or (tang ma)) hoi. ((hieu ve) or (hieu va)) tham thuc va hanh tai cau theo*.