Fig. 14

Behaviour of Eq.(7.2) with the parameters \(\sigma = 1, \; \gamma = 1, \; \tau =4, \; \theta = -1, \; \alpha = -2, \; d = 8 \;\) and \(\;k = -1.2\) , with initial values (0.7, 0.8) in blue, (0.5, 0.3) in red and (0.3, 0.1) in green.