Perhaps you should try some spelling variations:
thanh tai » thanh hai, thanh toan, doanh tai
hoc sach » hoc sinh, hoc anh
va thanh » gia thanh, ban thanh, va tinh
hieu cua » hieu qua, dieu cua, bieu cua
cac lop » cac hop, cac loai
ca viet » va viet, co viet, hoa viet
hoc cac » hoc cao
ang xa » lang xa, mang xa, dang xay
ty ang » ty xang, ty hang, ty anh
tai ca » tai cac, tai cao, tai cua
cac lo » cac co, cac bo, cac ho

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((hoc sach) or (hoc cac)) ty ang xa hoi. hieu cua ((cac lo) OR (cac lop)) va thanh tai ca viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((hoc sach) OR (hoc cac)) ty ang xa hoi. hieu cua ((cac lo) OR (cac lop)) va thanh tai ca viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((hoc sach) or (hoc cac)) ty ang xa hoi. hieu cua ((cac lo) OR (cac lop)) va thanh tai ca viet".
• Adding a wildcard symbol may retrieve word variants: ((hoc sach) or (hoc cac)) ty ang xa hoi. hieu cua ((cac lo) OR (cac lop)) va thanh tai ca viet*.