Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
lang van » dang van, tang van, hoang van
su sach » so sach, vu sach
mai duc » mai dich, mai quoc, mai dung
cai duc » cao duc, hoai duc, chi duoc
tang ma » mang may, tang van
vi cua » vai cua, di cua
cua tu » cua tuc, cua su, cua cu

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

• Performing a fuzzy search may retrieve terms with similar spellings: su sach y ((tang ma) or (lang van)) hoi. hieu qua ((cai duc) OR (mai duc)) van hanh vi cua tu~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach y ((tang ma) OR (lang van)) hoi. hieu qua ((cai duc) OR (mai duc)) van hanh vi cua tu*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach y ((tang ma) or (lang van)) hoi. hieu qua ((cai duc) OR (mai duc)) van hanh vi cua tu*".