瑜伽師地論略纂 8.140

8.140

又論云「中身、表身」，下文云「劣身、中身」，二中身何別？內身名中身，與表身相對；處中名中身，三品相對也。

Furthermore, the treatise speaks of "middle body, surface body," and below it speaks of "inferior body, middle body." What is the difference between the two "middle bodies"? The internal body is called the middle body, in contrast to the surface body; being intermediate is called the middle body, in contrast to the three grades.