Modelling the distribution of stamp paper thickness via finite normal mixtures: The 1872 Hidalgo stamp issue of Mexico revisited

Izenman and Sommer (1988) used a non-parametric Kernel density estimation technique to fit a seven-component model to the paper thickness of the 1872 Hidalgo stamp issue of Mexico. They observed an apparent conflict when fitting a normal mixture model with three components with unequal variances. This conflict is examined further by investigating the most appropriate number of components when fitting a normal mixture of components with equal variances.

The Anatomy of an International Cartel: Cyanide 1897-1927

The development of a new product or a new process, if adopted by the market, may generate a number of economic processes including secondary innovations to promote the exploitation of the new discovery. Such technological advances may also promote new industrial ventures which may exist over many decades, enhancing economic development. The history of the adoption of the cyanide process for the extraction of gold from its ores exemplifies such developments. One outcome was the formation of an international cyanide cartel.