6IANGV. NGV Count- Ranked Numerically As at December 2008 [ EB/OL]. [ 2008 - 12 - 30 ]. http://www, iangv. org/stats/NGV - Statistics08. htm.
7Ristovski Z D, Morawska L, Hitchins J. Particle emissions from compressed natural gas engines [ J ]. Journal of Aerosol Science, 2000(4) :403 -413.
8Schifter I, Diaz L, Lopez -Salinas E. Potential impacts of compressed natural gas in the vehicular fleet of Mexico City [ J ]. Environmental Science and Technology, 2000 ( 1 ) : 2100 - 2104.
9Ristovski Z, Morawska L, Ayoko G A. Emissions from a vehicle fitted to operate on either petrol or compressed natural gas [ J ]. Science of the Total Environment, 2004 ( 5 ) : 179 - 194.
