Brandl, S., W. Falk, T. Rötzer, and H. Pretzsch. “Assessing Site Productivity Based on National Forest Inventory Data and Its Dependence on Site Conditions for Spruce Dominated Forests in Germany”. Forest Systems, Vol. 28, no. 2, Sept. 2019, p. e007, doi:10.5424/fs/2019282-14423.