Perhaps you should try some spelling variations:
dan hanh » dang hanh, dan khanh, dan thanh
hieu van » hieu va, thien van, lieu va
nam thuc » nam thuoc, am thuc, nam thu
thuc dan » thuc hanh, hoc dan, thuc vat
su sach » so sach, vu sach
ky sang » ky nang, ky dang, ky tang
sang ma » tang ma, nang ma, sang tao
hieu ve » hieu va
va viet » san viet, mai viet, dao viet
sach ky » sac ky, sach y, sach ty
ma hoi » mai hoi, xa hoi, ma hoa

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 sang ma hoi. ((hieu ve) or (hieu van)) nam thuc dan hanh vi ((va viet) or (hoa viet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky sang ma hoi. ((hieu ve) OR (hieu van)) nam thuc dan hanh vi ((va viet) OR (hoa viet)).
• Adding a wildcard symbol may retrieve word variants: su sach ky sang ma hoi. ((hieu ve) or (hieu van)) nam thuc dan hanh vi ((va viet) or (hoa viet))*.