Perhaps you should try some spelling variations:
nham thuc » nhan thuc, nam thuc, pham thuc
toc sach » hoc sach, doc sach, thuoc sach
hieu van » hieu va, thien van, lieu va
danh sai » dung sai, danh bat, danh dau
vat danh » va danh, van danh, luat danh
nham thu » nam thu, pham thu, nhan thuc
lang xa » lang ha, dang xay, lang van
ky lang » ky nang, ky dang, ky tang
hoc cac » hoc cao
sai cua » dai cua, hai cua, lai cua
cua tre » cua te, cuu tre, cua triet

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) or (hoc cac)) ky lang xa hoi. hieu van ((nham thuc) OR (nham thu)) vat danh sai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (hoc cac)) ky lang xa hoi. hieu van ((nham thuc) OR (nham thu)) vat danh sai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) or (hoc cac)) ky lang xa hoi. hieu van ((nham thuc) OR (nham thu)) vat danh sai cua tre".
• Adding a wildcard symbol may retrieve word variants: ((toc sach) or (hoc cac)) ky lang xa hoi. hieu van ((nham thuc) OR (nham thu)) vat danh sai cua tre*.