Smith,J.E., Molina,R., Huso,M.M.P., Luoma,D.L., McKay,D., Castellano,M.A., Lebel,T. and Valachovic,Y., Species richness, abundance, and composition of hypogeous and  epigeous ectomycorrhizal fungal sporocarps in young, rotation-age, and old-growth stands of Douglas-fir (Pseudotsuga menziesii) in the Cascade Range of Oregon, USA. Can. J. Bot. 80, 186-204 (2002). https://www.ncbi.nlm.nih.gov/nuccore/EU525976