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
thuc dao » thuc dan, thuc day, chuc dao
cau tren » cu tren, dau tren, ca tren
sach ky » sac ky, sach y, sach ty
ky lang » ky nang, ky dang, ky tang
lang xa » lang ha, dang xay, lang van
dao van » do van, dang van
van hai » van ha, van chat, van hanh
cuu tre » cua tre, cau treo

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 ky lang xa hoi. hieu van nam thuc dao van hai ((cuu tre) or (cau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky lang xa hoi. hieu van nam thuc dao van hai ((cuu tre) OR (cau tren)).
• Adding a wildcard symbol may retrieve word variants: toc sach ky lang xa hoi. hieu van nam thuc dao van hai ((cuu tre) or (cau tren))*.