Perhaps you should try some spelling variations:
hieu quan » hieu qua, lieu quan, thien quan
cau tren » dau tren, ca tren, cau treo
vat hanh » vat thanh, van hanh, va hanh
cau thuc » cau truc, cuu thuc, can thuc
lang van » dang van, tang van, hoang van
quan cau » quang cao, toan cau, quan ha
hanh va » hang va, hanh vi
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
lang xa » lang ha, dang xay
cu tren » tu tren, dua tren

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