Listed articles are in PDF form, and some are huge.
Pyrodwarf info may be at .../books/596/596_52.htm
("New Pear Rootstocks from Geisenheim)
I found a few other titles by searching "Pyrodwarf" in the ISHS internal
search-engine.
Another useful article might be at yahoo-search of
Pear Rootstock & Cultivar Research at the OSU Mid-Columbia Agricultural
Research & Extension Center [might have to use 'and' instaed of '&']
I'm sorry I can't report on these, but I don't know when I'll have access to
a computer which can handle them. Good luck/ have fun.