Dr. Edwin Frey in Switzerland grew seeds of the Sanford Citrange and kept only those with non-trifoliate leaves, Sanford is trifoliate.
These non trifoliate leaved seedlings were almost certainly hybrids with true, edible citrus plants where the Sanford Citrange seed plants were located in America.
Growing them on to fruiting has produced some interesting and pretty cold tolerant fruiting plants.
Venasca is more vigorous than Curafora and produces larger fruit that are similar to a grapefruit.
Its leaves are not trifoliate and also similar to grapefruit with a large petiole.
Definitely another one for the hardy Citrus testers.