HEIER. S, KLEINKAUF W., SACHAU J.
Power Conditioning - The Link between Solar Conversion and Consumer

Advances in Solar Energy (Volume 9). An Annual Review of Research and  Development. American Solar Energy Society Boulder, USA 1994.P.161-244.

HEIER. S. ; DA COSTA, J. P. ; MESSOLL, K. ; VALOV, B.
Grid Connected Systems: Interconnection, Transmission and Generation

Wind Energy International 2011/ 2012. World Wind Energy Acciciation / WWEA 2011. Bonn, Germany.