Klein cordial trees and odd cyclic cordial friendship graphs. - William Q. Erickson; Daniel Herden; Jonathan Meddaugh; Mark Roger Sepanski; Isaac Echols; Cordell Hammon; Jorge Marchena-Menendez; Jasmin Mohn; Blanca Radillo-Murguia; Indalecio Ruiz-Bolanos (Discret. Math., 2023)