Witt, Detlev MPI for Comparative and International Private Law, Max Planck Society;
https://max-eup2012.mpipriv.de/index.php/State_Aid_Law (Any fulltext)
Witt, D. (2012). State Aid Law. In J. Basedow, K. J. Hopt, & R. Zimmermann (Eds.), Max Planck Encyclopedia of European Private Law (pp. 1592-1597). Oxford: Oxford University Press.