See for example:
Fisher, Redwood, บ.ก. (August 1846). "Statistics of the State of New-York". Fisher's National Magazine and Industrial Record. 3 (3): 234. สืบค้นเมื่อ 17 August 2013. [...] the three learned professions of divinity, law, and medicine [...]
(1961) 2 The Industrial and Labour Law Digest, 1926-1959, Annotated 668; Sharma and Goyal, Hospital Administration And Human Resource Management, 5th Ed, PHI Learning, p 445.
