Jieming Ma Ka Lok Man T. O. Ting Nan Zhang Sheng-Uei Guan Prudence W. H. Wong DEM: Direct Estimation Method for Photovoltaic Maximum Power Point Tracking. 537-544 2013 ITQM https://doi.org/10.1016/j.procs.2013.05.069 conf/itqm/2013 db/conf/itqm/itqm2013.html#MaMTZGW13