What does the abbreviation
mean in the context of historiography and archival science?
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: