What does the abbreviation "adhib." mean in historiography or archival science?

Question

What does the abbreviation

adhib.

mean in the context of historiography and archival science?

Remarks.

• This question is not about the meaning in medicine. This is easy to look up.

• Of course, literally it seems to mean 'to be administered/used', so my guess is that the abbreviation is used to emphasize what part of the given reference is relevant to the topic at hand.

• An example of the use I am asking an explanation of is to be found in the book

James C. Albisetti, ''Secondary School Reform in Imperial Germany'' Princeton University Press, 2014 ISBN 1400853087 380 pages

where e.g. on page 229 the abbreviation is used in a footnote:

Answer 1

It is short for adhibendum. I think the English equivalent would be something along the lines of "annex" or "appendix". As in, "Appendix B, Vol II, Proceedings of the School Conference of 1891".

I don't believe this is a general history convention. As far as I can determine, it's mainly a German usage; the example you gave is also citing a German publication.