@unpublished{TUW-120489, author = {Todorova, Sonya and Hobiger, Thomas and Schuh, Harald}, title = {Using GPS and satellilte altimetry for combined Global Ionosphere Maps}, year = {2006}, note = {poster presentation: COSPAR 2006, Beihjng, China; 2006-07-16 -- 2006-07-23} }