Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
hieu van » hieu va, thien van, lieu va
hanh tai » thanh tai, hang tai, han tai
cam thuc » am thuc, nam thuc, cam thu
va hanh » van hanh, va thanh, va danh
thuc va » thuc vat, thuc dan, thuc day
su hien » su kien, su tien, thu hien
hieu ve » hieu va
lang xa » lang ha, dang xay, lang van
nang xa » nang x, nang ma, mang xa
tai su » tai so, tai tu, lai su

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 y ((nang xa) or (lang xa)) hoi. ((hieu ve) OR (hieu van)) cam thuc va hanh tai su hien~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach y ((nang xa) OR (lang xa)) hoi. ((hieu ve) OR (hieu van)) cam thuc va hanh tai su hien.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach y ((nang xa) or (lang xa)) hoi. ((hieu ve) OR (hieu van)) cam thuc va hanh tai su hien".
• Adding a wildcard symbol may retrieve word variants: thu sach y ((nang xa) or (lang xa)) hoi. ((hieu ve) OR (hieu van)) cam thuc va hanh tai su hien*.