High-speed video and electromagnetic analysis of two natural bipolar cloud-to-ground lightning flashes - Saraiva, A. C. V; Campos, L. Z. S; Williams, E. R; Zepka, G.S.; Alves, J.; Pinto Jr., Osmar; Heckman, S.; Buzato, T. S.; Bailey, J. C.; Rodriguez, Carlos Augusto Morales; Blakeslee, R. J. (Journal of Geophysical Research: Atmospheres, 2014)