Evolution of vehicle emission factors in a megacity affected by extensive biofuel use: results of tunnel measurements in São Paulo, Brazil - Nogueira, Thiago; Kamigauti, Leonardo Yoshiaki; Pereira, Guilherme Martins; Calderon, Mario Eduardo Gavidia; Espinosa, Sergio Ibarra; Oliveira, Guilherme Librete de; Miranda, Regina Maura de; Vasconcellos, Pérola de Castro; Freitas, Edmilson Dias de; Andrade, Maria de Fátima (Environmental Science and Technololy, 2021)