Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
cam thuc » am thuc, nam thuc, cam thu
hanh tai » thanh tai, hang tai, han tai
mang xa » mang may, dang xay, mang cua
lang xa » lang ha, dang xay, lang van
hieu ve » hieu va, hieu van
thuc va » thuc vat, thuc dan, thuc day
va hanh » van hanh, va thanh, va danh
su hien » su kien, su tien, thu hien
ve cam » ve cham, ve cac, va cam
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 ((mang xa) or (lang xa)) hoi. hieu ve cam thuc va hanh tai su hien~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach y ((mang xa) OR (lang xa)) hoi. hieu ve cam thuc va hanh tai su hien.
• Adding a wildcard symbol may retrieve word variants: thu sach y ((mang xa) or (lang xa)) hoi. hieu ve cam thuc va hanh tai su hien*.