Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
hanh tai » thanh tai, hang tai, han tai
cam thuc » am thuc, nam thuc, cam thu
nang xa » nang x, nang ma, mang xa
su hien » su tien, thu hien, nhu hien
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
ve cam » ve cham, ve cac, va cam
kien » bien, vien, tien

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