Perhaps you should try some spelling variations:
cac thuc » cach thuc, cac thu, can thuc
thuc day » thuc dan, thuc vat
day hanh » day nhanh, day thanh, dao hanh
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
nang co » nang cao, nang doc, nang noi
lang ra » lang ha, lang xa, lang va
qua cac » cua cac
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: su sach ky ((nang co) or (lang ra)) hoi. hieu qua cac thuc day hanh vi ((cua tu) or (qua su))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky ((nang co) OR (lang ra)) hoi. hieu qua cac thuc day hanh vi ((cua tu) OR (qua su)).
• Adding a wildcard symbol may retrieve word variants: su sach ky ((nang co) or (lang ra)) hoi. hieu qua cac thuc day hanh vi ((cua tu) or (qua su))*.