Stability of the interstellar hydrogen inflow longitude from 20 years of SOHO/SWAN observations D. Koutroumpa, E. Quémerais, O. Katushkina, R. Lallement, J.-L. Bertaux and W. Schmidt A&A, 598 (2017) A12 Published online: 24 January 2017 DOI: 10.1051/0004-6361/201629840