found: Cist, C. Sketches and statistics of Cincinnati, 1859:plate recto (Ehrgott & Forbriger, SW corner 4th & Walnut sts., Cincinnati, O.)
found: Groce, G. N.Y. Hist. Soc's dict. of artists in Amer., 1957:(Ehrgott & Forbriger, lithographers of Cincinnati, Ohio, 1857 & after; partnership of Peter Ehrgott & Adolf Forbriger)
found: Last, J. Color Explosion ... 2005:page 74 (The parent firm was founded in 1856 by Peter Ehrgott... and Adolph Forbriger.)
found: Williams, C. Williams' Cincinnati Directory, City Guide and Business Mirror, 1859:page 111 (Ehrgott & Forbriger (Peter E. & Adolph F.,) Lithographers)
found: Williams, C. Williams' Cincinnati Directory, City Guide and Business Mirror, 1860:page 124 (Ehrgott, Forbriger & Co. (Peter E. & Adolph F.,) Lithographers)