Perhaps you should try some spelling variations:
hoc sach » hoc sinh, hoc cac, hoc anh
hieu van » hieu va, thien van, hieu ve
dinh vit » dinh viet, dinh vi, dinh vat
sach ky » sac ky, sach y, sach ty
cao hoi » cau hoi, co hoi, cao hoc
ca tren » cau tren, cu tren, la tren
luc va » tuc va, loc va
vit ca » viet ca, viet cau

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

• Performing a fuzzy search may retrieve terms with similar spellings: hoc sach ky nang cao hoi. ((hieu van) OR (lieu va)) cau ((luc va) or (duc va)) dinh vit ca tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc sach ky nang cao hoi. ((hieu van) OR (lieu va)) cau ((luc va) OR (duc va)) dinh vit ca tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc sach ky nang cao hoi. ((hieu van) OR (lieu va)) cau ((luc va) or (duc va)) dinh vit ca tren".
• Adding a wildcard symbol may retrieve word variants: hoc sach ky nang cao hoi. ((hieu van) OR (lieu va)) cau ((luc va) or (duc va)) dinh vit ca tren*.