Letter of 20 September 1971 from The Warsaw Photochemical Works FOTON [Warszawskie Zaklady Fotochemiczne FOTON] in Warsaw (Warszawa, Poland) addressed to Prof. W. Markocki. It was signed by Mikołaj Iliński, author of important photographic publications - "Materiały fotograficzne czarno-białe" ["Photographic Black and White Materials"] and "Materiały fotograficzne barwne" ["Photographic Color Materials"].