Perhaps you should try some spelling variations:
dan khanh » dang khanh, van khanh, dat khanh
khanh dao » hanh dao, lanh dao, thanh dat
nam thuc » nam thuoc, am thuc, nam thu
thuc dan » thuc hanh, hoc dan, thuc vat
toc sach » hoc sach, doc sach, thuoc sach
hieu van » hieu va, thien van, lieu va
cua tre » cua te, cua triet, dua tren
su sach » so sach, vu sach
lang xa » lang ha, dang xay, lang van
ky lang » ky nang, ky dang, ky tang
cuu tre » cau tren, 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: ((su sach) or (toc sach)) ky lang xa hoi. hieu van nam thuc dan khanh dao ((cua tre) OR (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((su sach) OR (toc sach)) ky lang xa hoi. hieu van nam thuc dan khanh dao ((cua tre) OR (cuu tre)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((su sach) or (toc sach)) ky lang xa hoi. hieu van nam thuc dan khanh dao ((cua tre) OR (cuu tre))".
• Adding a wildcard symbol may retrieve word variants: ((su sach) or (toc sach)) ky lang xa hoi. hieu van nam thuc dan khanh dao ((cua tre) OR (cuu tre))*.