Modelling of the shape of red heartwood in beech trees (Fagus sylvatica L.) based on external tree characteristics Holger Wernsdörfer, Gilles Le Moguédec, Thiéry Constant, Frédéric Mothe, Gérard Nepveu and Ute SeelingAnn. For. Sci., 63 8 (2006) 905-913DOI: https://doi.org/10.1051/forest:2006074