Historical notes of filter designs?
Along the line as Fat32's suggestion to consult IEEE papers, you might try to obtain a copy of "Digital Signal Processing" (IEEE Press Selected Reprint Series), Edited by: Lawrence R. Rabiner and Charles M. Rader, published by: IEEE press (1972).



That book contains reprints of many early (starting around the middle 1960s), and influential, scholarly papers on digital filtering. And of course those early papers contain references to even earlier papers.