How many different types of German and Austrian Notgeld are there?

I am very busy with banknotes from the Republic of China issued before 1950 and there are around 5175 catalogued of them according to the Shanghai Encyclopedia, however I am not as familiar with German and Austrian Notgeld and don't know any standard catalogues of them.

I know that during the 1920's a lot of German and Austrian towns started issuing "Notgeld" purely to cash in on banknote collectors so I would think that older catalogues in the public domain from the 1920's written by collectors must exist, right?

Colnect lists 17,137 for German notgeld and 6,794 for Austrian notgeld.