Perhaps you should try some spelling variations:
hieu quan » hieu qua, lieu quan, thien quan
quan cau » quang cao, toan cau, quan ha
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
ky tang » ky nang, ky dang, kho tang
tang xa » trang xa, tang ma, lang xa
truc va » thuc va, trung va
hanh va » hang va, hanh vi
cu tren » tu tren, dua tren
va cu » va cau, va chu, va su

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 tang xa hoi. hieu quan cau ((truc va) or (thuc vat)) hanh va cu tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky tang xa hoi. hieu quan cau ((truc va) OR (thuc vat)) hanh va cu tren.
• Adding a wildcard symbol may retrieve word variants: su sach ky tang xa hoi. hieu quan cau ((truc va) or (thuc vat)) hanh va cu tren*.