Then in 1969 during his time at University of Wisconsin-Madison, Virasoro successfully generalized Veneziano's theory and discovered a formula (the Virasoro-Shapiro amplitude) which described the scattering of closed strings.
Later in 1969, during his tenure at University of Wisconsin-Madison, Virasoro successfully broadened Veneziano's theory and discovered a formula (the Virasoro-Shapiro amplitude) that explained the scattering of closed strings.