Ponderosa lemon
The ponderosa lemon originated in roughly 1887, and is believed to come from a chance seedling grown in Hagerstown, Maryland. It was later named and introduced to the nursery trade in 1900. Though often referred to as a cross between the lemon and citron, a recent genomic analysis showed it to solely contain pomelo ("Citrus maxima") and citron ("Citrus medica") DNA, perhaps being an F2 hybrid. Thus they cannot derive from true lemons, which have a mandarin orange component.
Kabbad
The Kabbad refers to a citron-like fruit or citrus hybrid which was first described in 1963 by the Moroccan professor Henri Chapot, in his article named ""Le Cédrat Kabbad et deux autres variétés de cédrat"", who remarked it to be a biological hybrid between the citron and the orange sourcing from Damaskus, Syria.
Following is from The Citrus Industry vol. 1 Chap.4: