"Polikarpov U-2/Po-2". Flying Heritage & Combat Armor Museum. Friends of Flying Heritage. Archived from the original on 19 April 2017. Retrieved 2 May 2017.
"Polikarpov U-2/Po-2". Flying Heritage & Combat Armor Museum. Friends of Flying Heritage. Archived from the original on 19 April 2017. Retrieved 2 May 2017.