Reference

Herbert Wilfried Bennert, Rodolfo E. G. Pichi Sermolli, Helga Rasbach, Kurt Rasbach, Thaddäus [Tadeus] Reichstein (1988-1991): Asplenium x helii Lusina the valid name for the hybrids between A. petrarchae (Guérin) DC. and A. trichomanes L. (Aspleniaceae, Pteridophyta) I. Nomenclatural notes – Bauhinia – 9: 103 - 106.