Endnote abbr. meaning "same as before" (4)
I believe the answer is:
ibid
(Other definitions for ibid that I've seen before include "(When citing a reference) in the same place (abbr)" , "In the same place (L)" , "'In the same place as previously mentioned, in short (4)'" , "(When citing a reference) in the same place (Latin)" , "Briefly, in the same book or passage" .)