ERRATUM. In the original published version of Table 1, there was an error in the first equation. The final character in the equation, N2, should not appear in the equation. The correct equation is

dE1/dt = I - b1E1 + eE1

The corrected table, in which the N2 has been removed, is provided in full below.

TABLE 1 (corrected) :     Example model of an economic system, E, interacting with a natural system, N. The combined system is diagrammed in Fig. 1.


dE1/dt = I - b1E1 + eE1, E1(.) = 10
dE2/dt = b1E1 - b2E2 - eE2, E2(.) = 10

dN1/dt = P - a1N1N2 - a2N1, N1(.) = 315.23
dN2/dt = a1N1N2 - eE1 - a3N2N3 + a4N4N2, N2(.) = 316.23
dN3/dt = a3N2N3 - a5N3N4, N3(.) = 631.46
dN4/dt = a2N1 + a5N3N4 + eE2 - a4N4N2 - a6N42, N4(.) = 316.23

I = 1.0
b1 = 0.1 = b2
e = 0.0
P = 1000
a1 = 0.01 = a2 = a3 = a4 = a5 = a6