Research Discussion Paper – 1974 Equation (9)

\begin{array}{l} Δ XN = f (\overset{•}{W E}, \overset{•}{P N,} \overset{•}{P T}, \overset{•}{Q}, \overset{•}{t P,} \overset{•}{t Y,} \overset{•}{t I}) \\ \begin{array}{l} g_{1} > 0; & g_{2} < 0; & g_{3} > 0; & g_{4} < 0; \\ g_{5} > 0; & g_{6} > 0; & g_{7} < 0 \end{array} \end{array}