Time-focusing time-of-flight, a new method to turn a MAC-E-filter into a quasi-differential spectrometerA. Fulst, A. Lokhov, M. Fedkevych, N. Steinbrink and C. WeinheimerEur. Phys. J. C, 80 10 (2020) 956DOI: https://doi.org/10.1140/epjc/s10052-020-08484-9