Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
hieu van » hieu va, thien van, lieu va
toc sach » hoc sach, doc sach, thuoc sach
ky tang » ky nang, ky dang, kho tang
tang xa » trang xa, tang ma, lang xa
van cau » van dau, van hau, van chat
cau duc » cao duc, cau luc, chu duc
va hanh » van hanh, va thanh, va danh
cua tre » cua te, cuu tre, cua triet

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((te sach) or (toc sach)) ky tang xa hoi. hieu van cau duc va hanh vi ((cua tre) or (cau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (toc sach)) ky tang xa hoi. hieu van cau duc va hanh vi ((cua tre) OR (cau tren)).
• Adding a wildcard symbol may retrieve word variants: ((te sach) or (toc sach)) ky tang xa hoi. hieu van cau duc va hanh vi ((cua tre) or (cau tren))*.