Poppenhäger, K.; Robrade, J.; Schmitt, J. H. M. M.; Hall, J. C. (2009). “51 Pegasi – a planet-bearing Maunder minimum candidate”. Astronomy and Astrophysics508 (3): 1417–1421. doi:10.1051/0004-6361/200912945. ISSN0004-6361.
Poppenhäger, K.; Robrade, J.; Schmitt, J. H. M. M.; Hall, J. C. (2009). “51 Pegasi – a planet-bearing Maunder minimum candidate”. Astronomy and Astrophysics508 (3): 1417–1421. doi:10.1051/0004-6361/200912945. ISSN0004-6361.