European challenge:  east-west migration.
Kussbach
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D003710:Demography; D019049:Developed Countries; D004641:Emigration and Immigration; D005060:Europe; D007878:Legislation as Topic; D008913:Minority Groups; D011057:Politics; D011153:Population; D011154:Population Characteristics; D011157:Population Dynamics; D011640:Public Policy; D012036:Refugees; D014171:Transients and Migrants
Demographic Factors; Developed Countries; Europe; International Migration; Legislation; Migrants; Migration; Migration Policy; Minority Groups; Policy; Political Factors; Population; Population Characteristics; Population Dynamics; Population Policy; Refugees; Social Policy