Perhaps you should try some spelling variations:
toc sach » doc sach, thuoc sach, nuoc sach
danh doi » danh di, thanh doi, dung doi
hoc sach » hoc sinh, hoc cac, hoc anh
hieu va » lieu va, hieu qua
nang xa » nang x, lang xa, nang ma
vu nang » vuc nang, va nang, vu dang
ca tren » cau tren, cu tren, la tren
va cao » va cac, va co, va dao
luc va » tuc va, loc va
doi ca » doi cua, doi cay, duoi ca

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

• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (hoc sach)) vu nang xa hoi. hieu va cao ((luc va) OR (duc va)) danh doi ca tren~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) or (hoc sach)) vu nang xa hoi. hieu va cao ((luc va) OR (duc va)) danh doi ca tren~".
• Adding a wildcard symbol may retrieve word variants: ((toc sach) or (hoc sach)) vu nang xa hoi. hieu va cao ((luc va) OR (duc va)) danh doi ca tren*.