Perhaps you should try some spelling variations:
thien hoat » trien hoat, thien thuat, tien hoa
van thien » van tien, van hien, van chien
tinh quan » tinh quang, trinh quan, tin quan
hieu soat » hieu suat, hieu hoat, kiem soat
hieu luat » hieu qua
dung lan » dung luan, dung land, dung lam
quan lan » quan luan, quan lang, quan van
lan van » luan van, lang van, tan van

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: (( tin dung lan van thien hoat ) OR ( tinh quan lan van ((hieu soat) OR (hieu luat)) ))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( tin dung lan van thien hoat ) or ( tinh quan lan van ((hieu soat) OR (hieu luat)) ))~".
• Adding a wildcard symbol may retrieve word variants: (( tin dung lan van thien hoat ) or ( tinh quan lan van ((hieu soat) OR (hieu luat)) ))*.