多田, 鉄之助 (1972). たべもの日本史. Vol. 1. 新人物往来社., p.?, the author claims to have heard from the current successor to the restaurant that it was not the original innovator to put eel in jubako, and the old restaurant in Sanya was so named because the architecture resembled the jubako boxes
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うな重とうな丼、違いは名前と器だけ (Excite News, 22 July 2007; author: Wakako Tasachi (田幸和歌子)