Perhaps you should try some spelling variations:
hieu quan » hieu qua, lieu quan, thien quan
quan nam » quang nam, xuan nam, quan am
nam thuc » nam thuoc, am thuc, nam thu
dinh vi » dinh ve, dinh viet, dinh tri
danh vi » hanh vi, danh di, danh va
thuc va » thuc vat, thuc dan, thuc day
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
lang ra » lang ha, lang xa, lang va
nang co » nang cao, nang doc, nang noi
cua tu » cua tuc, cua su, cua cu

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach ky ((nang co) or (lang ra)) hoi. hieu quan nam thuc va ((danh vi) or (dinh vi)) cua tu~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky ((nang co) OR (lang ra)) hoi. hieu quan nam thuc va ((danh vi) OR (dinh vi)) cua tu.
• Adding a wildcard symbol may retrieve word variants: tu sach ky ((nang co) or (lang ra)) hoi. hieu quan nam thuc va ((danh vi) or (dinh vi)) cua tu*.