Leonard Fortuin, Five Popular Probability Density Functions: A Comparison in the Field of Stock-Control Models, The Journal of the Operational Research Society, Vol. 31, No. 10 (Oct., 1980), pp.

Probability density function is a statistical expression defining the likelihood of a series of outcomes for a continuous variable, such as a stock or ETF return.

Gary R. Skoog, James E. Ciecka, Probability Mass Functions for Years to Final Separation from the Labor Force Induced by the Markov Model, Journal of Forensic Economics, Vol. 16, No. 1 (Winter 2003), ...