op. cit.
Meaning. In the work already cited: used in footnotes to refer back to a source cited earlier.
Op. cit. is short for opere citato, “in the work cited”. In footnotes it refers to a work already cited in full, used with the author's name and a new page number, for example “Salmond, op. cit., p. 45”. It differs from ibid., which refers to the source cited immediately before.
Many modern citation styles, including the Oxford University Standard for Citation of Legal Authorities (OSCOLA), discourage op. cit. and prefer short-form citations with a cross-reference, because it forces the reader to search back for the full reference.
Example
In the footnote, “Mulla, op. cit., p. 112” pointed back to the full citation of Mulla's Hindu Law given earlier.