Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
hieu van » hieu va, thien van, lieu va
dai hai » dai han, dai hoi, dai tai
sach ky » sac ky, sach y, sach ty
van cac » van hac, van cau, van bac
ky sang » ky nang, ky dang, ky tang
va danh » va dinh, va dan, va hanh
danh vi » hanh vi, dinh vi, danh di
cuu tre » cau tren, cau treo
cua tre » cua te, cua triet, dua tren
ma hoi » mai hoi, xa hoi, ma hoa

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 sang ((ma hoi) or (dai hai)). hieu van cac nuoc va danh vi ((cuu tre) or (cua tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky sang ((ma hoi) OR (dai hai)). hieu van cac nuoc va danh vi ((cuu tre) OR (cua tre)).
• Adding a wildcard symbol may retrieve word variants: toc sach ky sang ((ma hoi) or (dai hai)). hieu van cac nuoc va danh vi ((cuu tre) or (cua tre))*.