... Michael Buddrus's "Totale Erziehung" is the best source. ... and it's in German only ;-).
Wim may be just a little modest since he does not mention his own book, Wim has written one of the best books about HJ - the book is mainly about triangles and shoulder straps, but there is a lot of other useful information in it. 784 pages of facts. The book is highly recommendable, I would not even do without it in my book collection. Here it is:
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Michael