The number of papers sharply declined after 1990 because of two simultaneous phenomena: first, scientists abandoned the field; second, journal editors declined to review new papers. Consequently, cold fusion fell off the ISI charts. Researchers who got negative results turned their backs on the field; those who continued to publish were simply ignored. A 1993 paper in Physics Letters A was the last paper published by Fleischmann, and "one of the last reports [by Fleischmann] to be formally challenged on technical grounds by a cold fusion skeptic."