Some properties of the ash from spruce needles
Wyttenbach A, Bajo S, Schleppi P, Bucher J & Tobler L
Wyttenbach, A., Bajo, S., Schleppi, P., Bucher, J., & Tobler, L. (1993). Some properties of the ash from spruce needles. Communications in Soil Science and Plant Analysis, 24(13-14), 1557-1566. https://doi.org/10.1080/00103629309368898