Kalb, Michael; Ramond, P. (1974-04-15). "Classical direct interstring action". Physical Review D. 9 (8). American Physical Society (APS): 2273–2284. doi:10.1103/physrevd.9.2273. ISSN0556-2821.
Kalb, Michael; Ramond, P. (1974-04-15). "Classical direct interstring action". Physical Review D. 9 (8). American Physical Society (APS): 2273–2284. doi:10.1103/physrevd.9.2273. ISSN0556-2821.