Brummitt 1971 - Heywood VH (1971) Flora Europaea: Notulae Systematicae ad Floram Europaeam spectantes: No. 8. Botanical Journal of the Linnean Society 64(1): 55-75. doi: 10.1111/j.1095-8339.1971.tb02134.x.
There is no corrections for Calystegia sepium subsp. spectabilis yet.