Perhaps you should try some spelling variations:
sach thien » sach thieu, sach tien, cach thien
thien nang » thien bang, thien dang, trien nang
cau tren » cu tren, dau tren, ca tren
hanh va » hang va, hanh vi
va hanh » van hanh, va thanh, va danh
tu sach » thu sach, su sach, te sach
hieu va » hieu qua
nang xa » nang x, lang xa, nang ma
cac tuc » cac toc, cac tu, cac tac
tuc va » thuc va, truc va, tuc xa
cua te » cua tu

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: tu sach thien nang xa hoi. ((hieu va) OR (lieu va)) cac tuc va hanh va ((cua te) OR (cau tren))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach thien nang xa hoi. ((hieu va) OR (lieu va)) cac tuc va hanh va ((cua te) or (cau tren))~".
• Adding a wildcard symbol may retrieve word variants: tu sach thien nang xa hoi. ((hieu va) OR (lieu va)) cac tuc va hanh va ((cua te) or (cau tren))*.