Effects of laser focusing and fluence on the analysis of pellets of plant materials by laser-induced breakdown spectroscopy - Carvalho, Gabriel Gustinelli Arantes de; Santos Júnior, Dário; Nunes, Lidiane Cristina; Gomes, Marcos da Silva; Leme, Flávio de Oliveira; Krug, Francisco José (Spectrochimica Acta Part B: Atomic Spectroscopy, 2012)