When making reference to the same source for a second or further time in your work, there is no need to repeat the reference in full. It is best to use the shortest form of reference that will still allow a reader to find the source. In most cases this will be the name of the author and a page reference (and the volume number in multi-volume works).
Millett, p. 21.
Mattingly, p. 80.
Where more than one work by the same author has been referred to in earlier notes, a short form of the title should also be included to avoid confusion. The form of writing of the abbreviated title should reflect that of the original note i.e. if the full title was in italics, the short form should also be.
Brown, 'Religious Dissent', p. 84.
Shaw, 'Circumcellions', p. 230.
Frend, Donatist Church, p. 90.