Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
lam duoc » nam duoc, luat duoc, lam thuoc
hieu van » hieu va, thien van, lieu va
chua tre » chua tri, cua tre, chua trieu
ty hang » ly hang, ty xang, thi hang
ty lang » tay lang, ty xang, tu lang
va hang » van hang, va lang, va hanh
va nang » van nang, da nang, cam nang
va chua » vua chua, ca chua, va chu
van lam » van nam

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 nang)) va chua 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 nang)) va chua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ((ty lang) OR (ty hang)) xa hoi. hieu van lam duoc ((va hang) or (va nang)) va chua 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 nang)) va chua tre*.