The question of simultaneouus or multiple discoveries was initiated
by Robert K Merton in "SINGLETONS AND MULTIPLES IN SCIENTIFIC
DISCOVERY - A CHAPTER IN SOCIOLOGY OF SCIENCE"
PROCEEDINGS OF THE AMERICAN PHILOSOPHICAL SOCIETY
105 (5): 470-& 1961. A huge literature in the "old" sociology of
science grew from this paper by Merton. You can trace the influence
of this paper at
http://www.garfield.library.upenn.edu/histcomp/merton_p-am-philo-
soc_v105_p470/
E. Roy Weintraub