found: Life, journals and correspondence of Rev. Manasseh Cutler, LL. D., 1888:t.p. (Robert Clarke & Co.; Cincinnati)
found: Journal of speculative philosophy, 1875:cover (Rob't. Clarke & Co.; publisher at Cincinnati)
found: History of book publishing in the United States, 1972-1981:v. 1, p. 488-489 (important general publishing house est. in Cincinnati in 1858 by Robert Clarke with partners R.D. Barney and J.W. Dale)
found: The publishing activities of Robert Clarke & Co., 1858-1909, 1940:leaf 36 (in 1894 Robert Clarke & co. was inc. as the Robert Clarke Company; final dissolution in a receiver's sale in 1909)