Perhaps you should try some spelling variations:
trinh quan » trinh luat, trinh han
tien soat » trien hoat, thien hoat, kiem soat
tinh quan » tin quan, sinh quan, trinh quang
hieu soat » hieu suat, hieu hoat, hieu luat
dan toan » van toan, dan than, manh toan
quan lan » quan luan, quan lang, quan van
van hieu » cao hieu
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: (( ((trinh quan) OR (tinh quang)) dan toan tien soat ) OR ( tinh quan lan van hieu soat ))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( ((trinh quan) OR (tinh quang)) dan toan tien soat ) or ( tinh quan lan van hieu soat ))~".
• Adding a wildcard symbol may retrieve word variants: (( ((trinh quan) OR (tinh quang)) dan toan tien soat ) or ( tinh quan lan van hieu soat ))*.