Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hieu van » hieu va, thien van, lieu va
quoc co » quoc cao, quoc cho, duoc co
cua tre » cua te, cua triet, dua tren
benh te » benh tre, benh ve, benh he
cuu tre » cau tren, cau treo
quoc bo » quoc bao, nuoc bo, quoc lo
van lam » van nam
lang xa » lang ha, dang xay, lang van
y lang » o lang, _ lang, tay lang

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 y lang xa hoi. hieu van lam ((quoc bo) or (quoc co)) benh te ((cua tre) OR (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach y lang xa hoi. hieu van lam ((quoc bo) OR (quoc co)) benh te ((cua tre) OR (cuu tre)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach y lang xa hoi. hieu van lam ((quoc bo) or (quoc co)) benh te ((cua tre) OR (cuu tre))".
• Adding a wildcard symbol may retrieve word variants: toc sach y lang xa hoi. hieu van lam ((quoc bo) or (quoc co)) benh te ((cua tre) OR (cuu tre))*.