Thank you very much for your answer, John.
I'm not searching for detailed studies, since I already have many papers (including those of R. Flemming) about ice accretion in my library. I'm only searching for an image to illustrate ice accretion in the context of rotorcraft in the motivation of my work. However, any of the publications in my library contains photographs of a quality comparable to those in sycamore's post. Therefore, I hope that sycamore will reply to provide information of the origin of the posted photographs.
Regards, MarSch