“Ulnaria ulna var. acus” (Ulnariaceae, Bacillariophyta), an invalid designation
D. M. Williams, and L. Ector
Notulae Algarum, vol. 87, pp. 1-2, 2019
http://www.notulaealgarum.com/documents/Notulae%20algarum%20No.%2087.pdf