sentences:  From 1970-1978 he was an applied Professor at Institut für Theoretische Geodäsie, University of Bonn and conducted lectures in astronomical and physical geodesy, including geoid determination by satellite geodesy and DTMs.In the years 1971–1974, 1976, 1978 and 1983, he returned to the National Geodetic Survey in Maryland to perform various research projects.In 1972 he was invited to teach at the Technical University Vienna (Austria) after the death of Karl Ledersteger, but he declined.