I had 2 questions relating to measuring global mean cortical thickness with the weighting factor of surface area 

1.) If this weighting is recommended, then shouldn't it be performed for each vertex in an exploratory whole brain group analyses (e.g., for one vertex in left hemi: lh.thickness*lh.surfarea)/(lh.surfarea).

2.) Are there any references that come to mind to cite in regards to this normalization technique?

I see that this following paper uses normalization (but was wondering if you would recommend any others):

Best,

Mike