Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
thuc dan » thuc hanh, hoc dan, thuc vat
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
nang ma » tang ma, sang ma, nang cao
hieu ve » hieu va
thuc va » thuc vat, thuc day
ca viet » va viet, co viet, hoa viet
vi ca » vit ca, li ca, va ca

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