Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
ban hang » ngan hang
hieu van » hieu va, thien van, lieu va
dai cau » dat cau, da cau, dai hau
te sach » toc sach
cam duc » cam xuc, cao duc, pham duc
sach ky » sac ky, sach y, sach ty
tao hoi » tao khoi, tay hoi, thao hoc
ky sang » ky nang, ky dang, ky tang
van cam » van nam, van lam, van cau

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

• If you are trying to use Boolean operators, they must be ALL CAPS: te sach ky sang ((tao hoi) OR (tao boi)). hieu van cam duc ((ban hanh) OR (ban hang)) dai cau tren~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach ky sang ((tao hoi) OR (tao boi)). hieu van cam duc ((ban hanh) or (ban hang)) dai cau tren~".
• Adding a wildcard symbol may retrieve word variants: te sach ky sang ((tao hoi) OR (tao boi)). hieu van cam duc ((ban hanh) or (ban hang)) dai cau tren*.