Valma, E., M. Tamosiunaite, S. Tamosiunas, M. Tamosiuniene, and M. Zilinskas. 2011. “Variation of Radio Refractivity With Height above Ground”. Elektronika Ir Elektrotechnika 111 (5):23-26. https://doi.org/10.5755/j01.eee.111.5.349.