Perhaps you should try some spelling variations:
nam thuc » nam thuoc, am thuc, nam thu
cua viet » ca viet, cua vat, cua dieu
su sach » vu sach
so sach » so sanh, bo sach, co sach
hieu he » hieu ve, hiem he, hieu le
thuc va » thuc vat, thuc dan, thuc day
va hanh » van hanh, va thanh, va danh
he nam » ha nam, nghe nam
x hoi » xa hoi, o hoi, x ho

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) or (so sach)) ky nang x hoi. hieu he nam thuc va hanh vi ((cua viet) OR (hoa viet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((su sach) OR (so sach)) ky nang x hoi. hieu he nam thuc va hanh vi ((cua viet) OR (hoa viet)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((su sach) or (so sach)) ky nang x hoi. hieu he nam thuc va hanh vi ((cua viet) OR (hoa viet))".
• Adding a wildcard symbol may retrieve word variants: ((su sach) or (so sach)) ky nang x hoi. hieu he nam thuc va hanh vi ((cua viet) OR (hoa viet))*.