Foukal, P.V. (1976). "The pressure and energy balance of the cool corona over sunspots". The Astrophysical Journal. 210: 575. Bibcode:1976ApJ...210..575F. doi:10.1086/154862.
Foukal, P.V. (1976). "The pressure and energy balance of the cool corona over sunspots". The Astrophysical Journal. 210: 575. Bibcode:1976ApJ...210..575F. doi:10.1086/154862.