Fan, S.M., D.J. Jacob, D.L. Mauzerall, D.D. Bradshaw, S.T. Sandholm, D.R. Blake, H.B. Singh, R. Talbot, G.L. Gregory, and G.W. Sachse (1994), Origin of Tropospheric NOx Over Subarctic Eastern Canada in Summer, J. Geophys. Res., 99, 16,867-16.