Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hieu van » hieu va, thien van, lieu va
lam duoc » nam duoc, luat duoc, lam thuoc
va lang » va nang, hoa lang
va hang » van hang, va nang, va hanh
van lam » van nam
ty hang » ly hang, ty xang, thi hang
ty lang » tay lang, ty xang, tu lang
cua tre » cua te, cuu tre, cua triet
va cua » va chua, via cua, ca cua

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

• Performing a fuzzy search may retrieve terms with similar spellings: toc sach ((ty lang) or (ty hang)) xa hoi. hieu van lam duoc ((va hang) or (va lang)) va cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ((ty lang) OR (ty hang)) xa hoi. hieu van lam duoc ((va hang) OR (va lang)) va cua tre.
• Adding a wildcard symbol may retrieve word variants: toc sach ((ty lang) or (ty hang)) xa hoi. hieu van lam duoc ((va hang) or (va lang)) va cua tre*.