Tiwari, Sanjiv Kumar Department Sun and Heliosphere, Max Planck Institute for Solar System Research, Max Planck Society;
Tiwari, S. K. (2012). On the Force-free Nature of Photospheric Sunspot Magnetic Fields as Observed from Hinode (SOT/SP). Astrophysical Journal, 744: 65. doi:10.1088/0004-637X/744/1/65.