No idea. Dozens of sketch books, though they also contain notes. Many (hundreds?) loose drawings on paper (good paper) and several hundred on cheap copier paper (That would be the bulk of the stuff posted here.
Just a few of the sketchbooks...
whow - i thougt I had many ... but Yours .. and till now, all I´ve seen are just the kind of drawings and sketches I like - would like to be so talented also.
Harald