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, thuc vat, trung va
va hanh » van hanh, va thanh, va danh
va chu » va che, va cau, va chi
va cu » va cau, va su, va tu

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 hanh ((va cu) OR (va chu)) 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 hanh ((va cu) OR (va chu)) tren".
• Adding a wildcard symbol may retrieve word variants: su sach ky lang xa hoi. hieu quan cau truc va hanh ((va cu) OR (va chu)) tren*.