 It is also not clear how important Franklin's unpublished results from the progress report actually were for the model-building done by Watson and Crick.After the first crude X-ray diffraction images of DNA were collected in the 1930s, William Astbury had talked about stacks of nucleotides spaced at 3.4 angström (0.34 nanometre) intervals in DNA.A citation to Astbury's earlier X-ray diffraction work was one of only eight references in Franklin's first paper on DNA.