Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hieu van » hieu va, thien van, lieu va
nam thuc » nam thuoc, am thuc, nam thu
lang xa » lang ha, dang xay, lang van
doi cua » dai cua, hoi cua
cua tre » cua te, cuu tre, cua triet
sach o » sach lo, sac o, sach y
o lang » hoa lang, hoi 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 o lang xa hoi. hieu van nam thuc ((va tinh) or (may tinh)) doi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach o lang xa hoi. hieu van nam thuc ((va tinh) OR (may tinh)) doi cua tre.
• Adding a wildcard symbol may retrieve word variants: toc sach o lang xa hoi. hieu van nam thuc ((va tinh) or (may tinh)) doi cua tre*.