Gammel, comp., The Laws of Texas 1822-1897, vol. 7, pp. 412, 414-415, 428-429; Reconstruction in Texas, Senate Miscellaneous Document 77, 41st Congress, 2nd Session, 1870 (serial 1408), pp. 38-79; Special Order 179, July 31, 1869, File 861-2, Adjutant General's Records (RG 401), Archives and Records Division, Texas State Library, Austin; Galveston Daily News, May 15, 1868; Colorado County Police [Commissioners] Court Minutes, Book 1862-1876, pp. 122, 123; Columbus Times, July 4, 1868. Zwiegel was among the delegates to the June 27, 1868 meeting of Colorado County's Democrats.