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 lang » ky nang, ky dang, ky tang
lang xa » lang ha, dang xay, lang van
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 lang xa hoi. hieu quan cau ((truc va) OR (thuc vat)) hanh va cu tren~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky lang 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 lang xa hoi. hieu quan cau ((truc va) OR (thuc vat)) hanh va cu tren*.