Usual formulas of continentality and their limits of validity

Equations given by W. Zenker in the last decade of the Nineteenth Century and later modified by other authors, characterizing the degree of continentality at a given place have the general form: k = mA/sin ϕ + n: where k = the continentality coefficient in per cent, A = average annual range of temperature at a given place, ϕ = geographical latitude, and m and n are constants.