Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
tay lang » tai lang, tay tang, tay quang
hieu van » hieu va, thien van, lieu va
hanh va » hang va, hanh vi
danh va » doanh va, anh va, dan va
nam xuc » cam xuc, nam xua, nam thuc
cua tre » cua te, cuu tre, cua triet
xuc va » duc va, tuc va, luc va

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 ((_ lang) or (tay lang)) xa hoi. hieu van nam xuc va ((danh va) OR (hanh va)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ((_ lang) OR (tay lang)) xa hoi. hieu van nam xuc va ((danh va) OR (hanh va)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ((_ lang) or (tay lang)) xa hoi. hieu van nam xuc va ((danh va) OR (hanh va)) cua tre".
• Adding a wildcard symbol may retrieve word variants: toc sach ((_ lang) or (tay lang)) xa hoi. hieu van nam xuc va ((danh va) OR (hanh va)) cua tre*.