(506) Duffield, John W., and F. I. Righter. 



1953. Annotated list of pine hybrids made at the Institute of Forest Genetics. U.S. 



Forest Serv. Calif. Forest and Range Exp. Sta. Res. Note 86, 9 pp. 



(507) and E. B. Snyder. 



1958. Benefits from hybridizing American forest tree species. J. Forest. 56: 809-815. 



(508) and Palmer Stockwell. 



1949. Pine breeding in the United States . U.S. Dep. Agr. Yearbook, Trees, 1949: 

 147-153. 



(509) Dunford, E. G. 



1954. Surface runoff and erosion from pine grasslands of the Colorado front range. 



J. Forest. 52: 923-927. 



(510) Dunnewald, T. J. 



1934. Soil factors in germination of pine seeds. Univ. Wyo. Sci. Pub. 1: 267-274. 



(511) Dunning, Duncan. 



1922. Relation of crown size and character to rate of growth and response to cutting 

 in western yellow pine. J. Forest. 20: 379-389. 



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1923. Some results of cutting in the Sierra forests of California. U.S. Dep. Agr. Bull. 

 1176, 26 pp. 



1928. A tree classification for the selection forests of the Sierra Nevada. J. Agr. Res. 

 36: 755-771. 



1928. Woodland thinning by preserving better trees often profitable. U.S. Dep. Agr. 

 Yearbook 1928: 624-625. 



1940. Direct seeding experiments in California. Pp. 18-24. IN: Experimental 



Direct Seeding by the Forest Service, M. A. Huberman, Ed. U.S. Forest 

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1942. A site classification for the mixed-conifer selection forests of the Sierra Nevada. 

 U.S. Forest Serv. Calif. Forest and Range Exp. Sta. Res. Note 28, 21 pp. 



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1945. Diameter-class volume tables for California old-growth timber. U.S. Forest 

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(518) and A. A. Hasel. 



1945. The Blacks Mountain Experimental Forest. A sustained yield experiment in 



ponderosa pine in northeastern California. U.S. Forest Serv. Calif. Forest 

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(519) and L. H. Reineke. 



1933. Preliminary yield tables for second growth stands in the California pine region. 

 U.S. Dep. Agr. Tech. Bull. 354, 23 pp. 



(520) Dutton, Walt L. 



1953. Forest grazing in the United States. J. Forest. 51: 248-251. 



(521) Dyrness, C. T., and C. T. Youngberg. 



1958. Soil -vegetation relationships in the central Oregon pumice region. First North 

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