Perhaps you should try some spelling variations:
pham thuc » phap thuc, pham chuc, nham thuc
van doan » van doanh, van toan, van hoan
te sach » toc sach
dau cua » dai cua, day cua, cau cua
va doan » va doanh, va dan, va don
vu pham » su pham, vi pham, vu kham
sach ky » sac ky, sach y, sach ty
hieu vu » hieu va, hieu ve, hieu su
dai hoi » dai hoc, dai hai, dai moi
mai hoi » mai khoi, lai hoi, mai doi
cua tre » cua te, cuu tre, cua triet

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 nang ((mai hoi) OR (dai hoi)). hieu vu pham thuc ((va doan) OR (van doan)) dau cua tre~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach ky nang ((mai hoi) OR (dai hoi)). hieu vu pham thuc ((va doan) or (van doan)) dau cua tre~".
• Adding a wildcard symbol may retrieve word variants: te sach ky nang ((mai hoi) OR (dai hoi)). hieu vu pham thuc ((va doan) or (van doan)) dau cua tre*.