North American Fruit Explorers mailing list at ibiblio

["Kieran &/or Donna" <holycow@frontiernet.net>]

Synonyms (alternative names) for Ziziphus jujuba: Rhamnus zizyphus, 
Ziziphus jujuba var. spinosa,  Ziziphus sativa,  Ziziphus spinosa,  Ziziphus 
vulgaris,  Ziziphus vulgaris var. spinosa,  Ziziphus zizyphus,  Zizyphus 
sativa

I think that the "wild sour jujube" is indeed the wild crabapple of the 
jujube world.  The tame ones have been selected and propagated for size and 
flavor.