Perhaps you should try some spelling variations:
va triet » va thiet, va trien, ve triet
thuc van » thuc vat, thuc dan, thuc va
dua tren » dung tren
hanh doi » thanh doi, hanh noi, hang doi
van hanh » van thanh, ban hanh, van anh
cam thuc » am thuc, nam thuc, cam thu
hieu ve » hieu va, hieu van
mang xa » lang xa, mang may, dang xay
so sach » so sanh, bo sach, co sach
ve cam » ve cham, ve cac, va cam

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

• Performing a fuzzy search may retrieve terms with similar spellings: so sach y ((mang xa) or (nang x)) hoi. hieu ve cam thuc van hanh doi ((dua tren) or (va triet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach y ((mang xa) OR (nang x)) hoi. hieu ve cam thuc van hanh doi ((dua tren) OR (va triet)).
• Adding a wildcard symbol may retrieve word variants: so sach y ((mang xa) or (nang x)) hoi. hieu ve cam thuc van hanh doi ((dua tren) or (va triet))*.