俱舍論頌疏論本 28.13

28.13

并上三近分，總名除色想者，前四根本無色，并上三無色近分，此七總名除去色想，空處近分未得此名，緣下地色，有色想故。

Regarding "Together with the upper three preliminary [stages], they are collectively called 'removal of the perception of form'": the former four root formless [attainments], together with the preliminary stages of the upper three formless [attainments]—these seven are collectively called "removal of the perception of form." The preliminary stage of the [sphere of] boundless space does not yet receive this name, because it takes the form of the lower level as its object and thus has perceptions of form.