Sorknæs, Peter, Henrik Lund, Anders N Andersen, and Peter Ritter. 2015. “Small-Scale Combined Heat and Power As a Balancing Reserve for Wind – The Case of Participation in the German Secondary Control Reserve”. International Journal of Sustainable Energy Planning and Management 4 (February). Aalborg, Denmark:31-42. https://doi.org/10.5278/ijsepm.2014.4.4.