http://tobaccodocuments.org/filters/2501224987-5003.html
Hausermann, M. "CIGARETTES A LA CARTE or How to play with filter efficiency, filter dilution and expanded tobacco in designing low- and very-low-tar cigarettes". 17 Jul 1980. Bates: 2501224987-2501225003.
http://tobaccodocuments.org/filters/2501224987-5003.html