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
lang xa » lang ha, dang xay, lang van
van lam » van nam
benh te » benh tre, benh he, benh theo
benh ve » benh va, benh vien, benh viem
cua tre » cua te, cuu tre, cua triet
sach o » sach lo, sac o, sach y
o lang » hoa lang, hoi lang
duoc o » duoc co, duoc do, duoc vo

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 o lang xa hoi. hieu van lam duoc o ((benh te) or (benh ve)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach o lang xa hoi. hieu van lam duoc o ((benh te) OR (benh ve)) cua tre.
• Adding a wildcard symbol may retrieve word variants: toc sach o lang xa hoi. hieu van lam duoc o ((benh te) or (benh ve)) cua tre*.