@article{Nicolls2009a, author = "M. J. Nicolls and M. C. Kelley and R. H. Varney and C. J. Heinselman", title = "Spectral observations of polar mesospheric summer echoes at 33 cm (450 MHz) with the Poker Flat Incoherent Scatter Radar", year = 2009 , journal = "J. Atmos Solar-Terr. Phys.", volume = 71, number = 6, pages = "662-674", keywords = "amisr, pfisr", doi = "10.1016/j.jastp.2008.04.019" }