Chinese to English Art/Literary Education / Pedagogy

I'm translating a list of works by a Chinese scholar and I found this term I don't know how to translate: 合卷本
Context:
教育大辞典（增订合卷本，主编），1998年，上海教育出版社。

增订 means "revised and enlarged", but what about 合卷本?

Previously in the list there is the same work in his first edition:
教育大辞典（12卷本，主编），1990—1992年，上海教育出版社。

Thanks!