Motocra, previously at www.motocra.com, had extensive and well-presented information on the Spanish motorcycle industry, with a focus on Ossa.
Much of the original site is available at the Wayback Machine:
https://web.archive.org/web/20090407085109/http://www.motocra.com/ossa/index.html
Efforts to contact the author have, to date, been fruitless.
The following was posted to Juan Porcar on Messenger, linked from a post on his FB page at https://www.facebook.com/1637734453/