By Karikari, S K, Mathew, I P, Onazi, O C
By The European Garden Flora Editorial Committee (Stanley Smith Horticultural Trust, Cambridge)
By Tim D. Davis, Bruce E. Haissig, Narendra Sankhla
By H.H. van der Borg, et al
By P.J. Salter, J.K.A. Bleasdale, others
By Gerd Krussmann, Michael E. Epp
By Gerd Krussmann
By The European Garden Flora Editorial Committee (University of Cambridge Botanic Garden)
By Roger Balls
By James L. Brewster (Horticulture Research International, Wellesbourne, UK)
By F.S. Hardy, G.D. Watson
By G. R. Dixon
By Richard J. Chancellor
By John E. Preece, Paul Read
By John W. Mastalerz
By James B. Beard
By Roderick Floud
By P.J. Salter, J.K.A. Bleasdale
By Mike Dash
By Jonathan Edwards
By Alan Bloom
By Carol R. Peterson
By Fiona Davison
By D.O'D. Bourke, etc.
By N. D. G. James (Oxford University)