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
dan vai » dan va, dan vat, den vai
cuu tre » cau tren, cau treo
dan tai » van tai, dan thi, han tai
cua tre » cua te, cua triet, dua tren
sach ky » sac ky, sach y, sach ty
thuc ca » thuc cua, thuc can, thuc cao
dang xa » dang xay, lang xa, dang ha
ky dang » ky nang, ky danh

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 dang xa hoi. hieu van nam thuc ca ((dan vai) or (dan tai)) ((cuu tre) or (cua tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky dang xa hoi. hieu van nam thuc ca ((dan vai) OR (dan tai)) ((cuu tre) OR (cua tre)).
• Adding a wildcard symbol may retrieve word variants: toc sach ky dang xa hoi. hieu van nam thuc ca ((dan vai) or (dan tai)) ((cuu tre) or (cua tre))*.