Apostolov, E. M., Geophysical Institute, Bulgarian Academy of Sciences, Sofia, Bulgaria

• Annals of Geophysics Vol. 37 No. 2 (1994) - OLD
  Solar cycle and seasonal behaviour of quasi two and rive day oscillations in the time variations of fOF2
  Abstract  PDF
• Annals of Geophysics Vol. 47 No. 2-3 Sup. (2004) - OLD
  Planetary and gravity wave signatures in the F-region ionosphere with impacton radio propagation predictionsand variability
  Abstract  PDF