Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
dua tren » dung tren
hanh di » hanh vi, hanh de, hang di
va hanh » van hanh, va thanh, va danh
cau luc » cau truc, cau phuc
cac luc » coc luc, cac nuoc, cac cuoc
hieu va » lieu va, hieu qua
lang xa » lang ha, dang xay, lang van
cu tren » tu tren

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 xa hoi. hieu va ((cac luc) OR (cau luc)) va hanh di ((dua tren) or (cu tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach _ lang xa hoi. hieu va ((cac luc) OR (cau luc)) va hanh di ((dua tren) OR (cu tren)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach _ lang xa hoi. hieu va ((cac luc) OR (cau luc)) va hanh di ((dua tren) or (cu tren))".
• Adding a wildcard symbol may retrieve word variants: toc sach _ lang xa hoi. hieu va ((cac luc) OR (cau luc)) va hanh di ((dua tren) or (cu tren))*.