Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
hieu van » hieu va, thien van, lieu va
manh hai » lanh hai, minh hai, thanh hai
cam thuc » am thuc, nam thuc, cam thu
nang xa » nang x, nang ma, mang xa
lang xa » lang ha, dang xay, lang van
sach ky » sac ky, sach ty, sach kem
van cam » van nam, van lam, van cau
thuc va » thuc vat, thuc dan, thuc day
va manh » van manh, va danh, va hanh
hai cau » hai chau, hai chu, hai hau

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: su ((sach ky) or (sach y)) ((nang xa) OR (lang xa)) hoi. hieu van cam thuc va manh hai cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach ky) OR (sach y)) ((nang xa) OR (lang xa)) hoi. hieu van cam thuc va manh hai cau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((sach ky) or (sach y)) ((nang xa) OR (lang xa)) hoi. hieu van cam thuc va manh hai cau tren".
• Adding a wildcard symbol may retrieve word variants: su ((sach ky) or (sach y)) ((nang xa) OR (lang xa)) hoi. hieu van cam thuc va manh hai cau tren*.