Published in Classical and Quantum Gravity.
The arXiv preprint was submitted on 19 October 2010. Journal venue: Classical and Quantum Gravity; journal DOI: 10.1088/0264-9381/27/23/233001.
Cited passages: Section 1.2, printed p. 2: geometrical optics, weak fields and slowly moving lenses; compact-object near-field propagation excluded; Section 2.2, printed pp. 15-16, equations (100)-(110): point-mass model, two roots, critical circle and magnification.
arXiv version 1 was submitted on 3 June 1996; version 2 was revised on 2 October 1997. The date printed by the dynamically regenerated PDF is not used as a publication date.
Cited passages: Section 2.1.3, pp. 8-9, equations (13)-(15), including the warning that lens-source angular diameter distance is not the difference of the observer distances.