Jonasson, Sven (1988). "Evaluation of the Point Intercept Method for the Estimation of Plant Biomass". Oikos. 52 (1): 101–106. doi:10.2307/3565988. JSTOR3565988.
Heady, Harold F.; Rader, Lynn (March 1958). "Modifications of the Point Frame". Journal of Range Management. 11 (2): 2. doi:10.2307/3894295. JSTOR3894295.
jstor.org
Jonasson, Sven (1988). "Evaluation of the Point Intercept Method for the Estimation of Plant Biomass". Oikos. 52 (1): 101–106. doi:10.2307/3565988. JSTOR3565988.
Heady, Harold F.; Rader, Lynn (March 1958). "Modifications of the Point Frame". Journal of Range Management. 11 (2): 2. doi:10.2307/3894295. JSTOR3894295.