Source:
* University of Fribourg (Switzerland, 1966)
* University of Chicago (US, 1966)
* University of Edinburgh (United Kingdom, 1979)
* University of Bologna (Italy, 1989)
* Goethe University Frankfurt (Germany, 1990)
* Louis Pasteur University (France, 1991)
* Harvard University (US, 1993)
* Scripps Research Institute (US, 2000)
* University of Innsbruck (Austria, 2010)