Perhaps you should try some spelling variations:
trinh luan » trinh luat, trinh quan, trinh han
quang lang » quan lang, quang dang, quang hoang
hieu soat » hieu suat, hieu hoat, hieu luat
lang van » dang van, tang van, hoang van
van hieu » cao hieu
van kien » van tien, van chien
van hien » van tien
tinh » dinh, minh, kinh

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: (( tinh quang lang van hieu soat ) OR ( trinh luan van ((van kien) OR (van hien)) toan ))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( tinh quang lang van hieu soat ) or ( trinh luan van ((van kien) OR (van hien)) toan ))~".
• Adding a wildcard symbol may retrieve word variants: (( tinh quang lang van hieu soat ) or ( trinh luan van ((van kien) OR (van hien)) toan ))*.