1. Bigg W S and T W Daniel 1978 Effects of nitrate, ammonium and pH on the growth of conifer seedlings and their production of nitrate reductase. Plant and Soil 50, 371–385.
2. Bowen G D 1973 Mineral nutrition of ectomycorrhizae.In Ectomycorrhizae: Their Ecology and Physiology. Eds. G C Marks and T T Kozlowski. Academic Press, NY, pp 151–205.
3. Bowen G D and S E Smith 1981 The effects of mycorrhizas on nitrogen uptake by plants. In Terrestrial Nitrogen Cycles. Eds. F E Clark and T Rosswall. Ecol. Bull (Stockholm) 33, 219–232.
4. Bremner J M 1965 Total nitrogen, Inorganic forms of nitrogen, Organic forms of nitrogen.In Methods of Soil Analysis. Ed. C A Black. Am. Soc. Agron., Madison, WI, pp. 1035–1049.
5. Gessel S P, T N Stoate and K J Turnbull 1969 The growth and behavior of Douglas-fir with nitrogenous fertilizer in western Washington. Inst. of Forest Prod. Contrib No. 7, Univ. of Washington, Seattle WA, 119 p.