EX-10.13 14 ex10-13.htm THIRTEENTH AMENDMENT TO PROMISSORY NOTES DATED AS OF APRIL 20, 2012 AMONG GROEN BROTHERS AVIATION, INC. AND LENDER D NAMED THEREIN ex10-13.htm
Exhibit 10.13
 
 
1
 
 
 
2
 
 
 
3
 
 
 
4
 
 
5