1. Anonymous . 1985. SAS User's guide: Statistics, 1985 edition, 958Cary, NC: SAS Institute Inc. USA
2. Ekström , H. 1989. Aspvirke—egenskaper och användning, Research notes no. 207 104Uppsala, Sweden: Swedish University of Agricultural Sciences, Department of Forest Products. (In Swedish.)
3. Ericson , B. 1959. A mercury immersion method for determining the wood density of increment core sections, Report no. 1 31Forest Research Institute of Sweden.