@inbook{Surdej_1987,
title={Mirages Caused by a Gravitational Lens},
ISBN={9789400937697},
url={http://dx.doi.org/10.1007/978-94-009-3769-7_57},
DOI={10.1007/978-94-009-3769-7_57},
booktitle={Exercises in Astronomy},
publisher={Springer Netherlands},
author={Surdej,
Jean},
year={1987},
pages={247–250} }