I would like to have statistics on Eastern European scientists working in Western Europe. 

I have found some related papers like [Brain Drain in the European Union: Facts & Figures](http://www.bridgingeurope.net/uploads/8/1/7/1/8171506/wp4_rethink_edu_braindrain_nedeljkovic.pdf) or [Emigration from Eastern Europe with a Focus on Brain Drain](http://pure.au.dk/portal/files/75142686/Luiza_Ionescu_Emigration_from_Eastern_Europe_with_a_focus_on_Brain_Drain.pdf) but these do not contain data material for knowing how many scientists move from Eastern Europe to Western Europe.

Could you help me finding a reliable data source on this?