Perhaps you should try some spelling variations:
trinh vat » trinh luat, sinh vat, trinh han
trinh van » trinh han, trinh quan, trinh toan
dang cong » dung cong
dat sach » mat sach, dat khach, ban sach
nam sach » ngan sach, nam danh, nam sao
cong san » cong tac
san toan » van toan, dan toan, manh toan
toan cau » toan cao, toan ban, toan tap

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: theo ((dat sach) OR (nam sach)) - hanh ((trinh vat) OR (trinh van)) dang cong san toan cau~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "theo ((dat sach) OR (nam sach)) - hanh ((trinh vat) or (trinh van)) dang cong san toan cau~".
• Adding a wildcard symbol may retrieve word variants: theo ((dat sach) OR (nam sach)) - hanh ((trinh vat) or (trinh van)) dang cong san toan cau*.