I tried to find the mentioned videos in reference [1] but couldn’t, apart from maybe this: cerf volant outdoor - YouTube
A mention of “whirling arm” in the paper, and a video of it: George Caley - The British inventor of the aeroplane, previously linked.
Here it is used to test a kite plane: TX-8.2 Flight - YouTube. And new videos from the same channel of a kite plane riding up and down a tether: WindiVator 1.0 - YouTube and a kite plane controlled by flight software: - YouTube
Related (control line flying; torqueless rotors): Random interesting links - #16 by Windy_Skies