Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
hieu van » hieu va, thien van, lieu va
thuc cao » thuoc cao, thuc co, thuc can
cau treo » cau theo, cau tren, cau triet
sach ky » sac ky, sach y, sach ty
nang xa » nang x, lang xa, nang ma
thuc ca » thuc cua, thuc can, thuc va
dan va » doan va, dan ca, han va

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

• Performing a fuzzy search may retrieve terms with similar spellings: doc sach ky nang xa hoi. hieu van nam ((thuc ca) or (thuc cao)) ((dan va) or (ban va)) cau treo~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc sach ky nang xa hoi. hieu van nam ((thuc ca) OR (thuc cao)) ((dan va) OR (ban va)) cau treo.
• Adding a wildcard symbol may retrieve word variants: doc sach ky nang xa hoi. hieu van nam ((thuc ca) or (thuc cao)) ((dan va) or (ban va)) cau treo*.