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

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