In this paper, we prove that in a simple model of income determination, when taking into account linear functions, the change rate for the gross domestic product (GDP) is equal to the quotient of the increase in investment and the sum of exogenous consumption plus the initial investment. This...

In the third decade of the 20th century, Lévi-Provençal discovered an Arab manuscript by the ishbili Ibn cAbdun, that dealt with the commercial and artisan practices in Seville at the end of the 11th century. In the document there were references to the offices and personages who had to...

The optimal capacity and location of a sequence of landfills are studied, and the interactions between both decisions are pointed out. Deciding the capacity of a landfill has some spatial implications, because it effects the feasible region for the rest of the landfills, and some temporal...