François Frison-Roche has asked me to post links to a couple of his publications. If you read French and you are interested in semi-presidentialism in Central and Eastern Europe, then this work is really invaluable.
La transition en Europe post-communiste: de l’utilité du «modèle semi-présidentiel»
In English there is quite a lot of excellent work on Central and Eastern Europe. One perhaps lesser-known book is by Thomas Sedelius. It is called The Tug-Of-War Between Presidents and Prime Ministers. Semi-presidentialism in Central and Eastern Europe. It is published by Orebro University, Sweden.