1. The ionospheric propagation of radio waves of frequency 16 kc/s over distances of about 540 km;Bain;Proc. IEE Pt. IV,1952
2. The ionospheric propagation of radio waves of frequency 16 kc/s over distances of about 200 km;Bracewell;Proc. IEE Pt. IV,1952
3. Periodic fading of VLF signals received over long paths during sunrise and sunset;Crombie;Radio Sci. J. Res. NBS,1964
4. Further observations of sunrise and sunset fading of very-low-frequency signals;Crombie;Radio Sci.,1966