Perhaps you should try some spelling variations:
"trinh dung luan van hieu hoat" » "trinh dung luan van hieu hoa", "trinh dung luan van thien hoat", "trinh dung luan van hieu luat", "trinh dung luan cao hieu hoat", "trinh dung quan van hieu hoat"
"tinh dung lan van tien soat" » "tin dung lan van tien soat", "tinh quang lan van tien soat", "tinh huong lan van tien soat", "tinh dung lan van trien hoat", "tinh dung lan van thien hoat", "tinh dung lan van kiem soat", "tinh dung land van tien soat", "tinh dung lam van tien soat", "tinh dung san van tien soat", "tinh dung lan toan tien soat", "tinh dung lan van tuan soat", "tinh dung lang van tien soat", "tinh dung tan van tien soat"

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

• Performing a fuzzy search may retrieve terms with similar spellings: (("trinh dung luan van hieu hoat") or ("tinh dung lan van tien soat"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("trinh dung luan van hieu hoat") OR ("tinh dung lan van tien soat"))*.
• Removing quotes may allow a broader search: (( trinh dung luan van hieu hoat ) or ( tinh dung lan van tien soat ))*.