ok, ask a specific question. The paper seems to lay-out the steps for making the Vn diagram pretty clearly. There is data included ("use Cn ...") that may be "red herrings" (I don't immediately see how it applies).
Do you understand how to draw the "stall curve" (the +ve left hand part of the envelope) ?
On a quick scan I'm not sure if they've defined Vc and Vd (but I'm sur they have).
"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.