Reference for TT_desai_fspmaps


I know there is a reference for Desikan-Killiany Atlas for cortical areas…
(Desikan et al., Neuroimage 2006 (31) pp. 968-980)
but I do not know what the reference is for the subcortical 40 areas using FreeSurfer,
which is TT_desai_fspmaps…

Is there any reference that I can use for this?