31. nespecifikovano Type: model:periodicalitem and TEXT Language: English Rights: http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
32. Publications of the Astronomical Institute of the Academy of Sciences of the Czech Republic Type: model:periodicalitem and TEXT Language: Czech Description: 26 and Methoda ionosférických prognos Rights: http://creativecommons.org/publicdomain/mark/1.0/ and policy:public