A datum reference can be along the straight edge of a design, known as datum surface, or a single datum point, often found in the corner of a design. In a circular shape, it would be around the ...
Baker, Malcolm, Xin Pan, and Jeffrey Wurgler. "The Effect of Reference Point Prices on Mergers and Acquisitions." Journal of Financial Economics 106, no. 1 (October 2012): 49–71.