Perhaps you should try some spelling variations:
nham thuc » nhan thuc, nam thuc, nham thu
cham tuc » pham thuc, tham thuc, cham soc
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
hieu ve » hieu va, hieu van
ky dang » ky nang, ky danh
cua tre » cua te, cuu tre, cua triet
ma hoi » mai hoi, xa hoi, me hoi
va don » va dong, va doc, va do
vi cua » vai cua, di cua

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach ky dang ((ma hoi) or (ma hoa)). hieu ve ((cham tuc) OR (nham thuc)) va don vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky dang ((ma hoi) OR (ma hoa)). hieu ve ((cham tuc) OR (nham thuc)) va don vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky dang ((ma hoi) or (ma hoa)). hieu ve ((cham tuc) OR (nham thuc)) va don vi cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ky dang ((ma hoi) or (ma hoa)). hieu ve ((cham tuc) OR (nham thuc)) va don vi cua tre*.