Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
van hanh » van thanh, ban hanh, van anh
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
sach ty » sach y, sach tu, sach thu
cua cau » cua cac, cua chu, cua can
cua cay » cua cac
cac vuc » cac vung, cac cuoc, cac quoc
hieu ve » hieu va, hieu van
hang co » hang cho, hang ca, nang co
ty hang » ly hang, ty xang, thi hang

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 ty hang co hoc. hieu ve ((cac vuc) or (cac nuoc)) van hanh vi ((cua cau) OR (cua cay))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc sach ty hang co hoc. hieu ve ((cac vuc) OR (cac nuoc)) van hanh vi ((cua cau) OR (cua cay))*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc sach ty hang co hoc. hieu ve ((cac vuc) or (cac nuoc)) van hanh vi ((cua cau) OR (cua cay))*".