Scanning tunneling microscopy study of a DNA fragment of known size and sequence Monique Marilley, Philippe Pasero, Alain Humbert, Samuel Granjeaud, Michel Dayez, Roger Pierrisnard and Bertrand Jordan Microsc. Microanal. Microstruct., 5 1 (1994) 47-56 DOI: 10.1051/mmm:019940050104700