@unpublished{TUW-120839, author = {Todorova, Sonya and Schuh, Harald and Hobiger, Thomas and Hernandez-Pajares, Manuel}, title = {Impact of the Combination of GNSS and Altlimetry Data on theDerived Global Ionosphere Maps}, year = {2007}, note = {talk: AGU Joint Assembly2007, Acapulca, Mexico; 2007-05-22 -- 2007-05-25} }