The shape of the radio wavefront of extensive air showers as measured with LOFAR gan Corstanje, A, Schellart, P, Nelles, A, Buitink, S, Enriquez, J, Falcke, H, Frieswijk, W, Horandel, JR, Krause, M, Rachen, J, Scholten, O, ter Veen, S, Thoudam, S, Trinh, T, van den Akker, M, Alexov, A, Anderson, J, Avruch, I, Bell, M, Bentum, M, Bernardi, G, Best, P, Bonafede, A, Breitling, F, Broderick, J, Bruegen, M, Butcher, H, Ciardi, B, de Gasperin, F, de Geus, E, de Vos, M, Duscha, S, Eisloeffel, J, Engels, D, Fallows, R, Ferrari, C, Garrett, M, Griessmseier, J, Gunst, A, Hamaker, J, Hoeft, M, Homeffer, A, Icobelli, M, Juette, E, Karastergiou, A, Kohler, J, Kondratiev, V, Kuniyoshi, M, Kuper, G, Maat, P, Mann, G, McFadden, R, McKay-Bukowski, D, Mevius, M, Munk, H, Norden, M, Orru, E, Paas, H, Pandey-Pommier, M, Pandey, V, Pizzo, R, Polatidis, A, Reich, W, Rottgering, H, Scaife, A, Schwarz, D, Smirnov, O, Stewart, A, Steinmetz, M, Swinbank, J, Tagger, M, Tang, Y, Tasse, C, Toribio, C, Vermeulen, R, Vocks, C, van Weeren, R, Wijnholds, S, Wucknitz, O, Yatawatta, S, Zarka, P