{ diff(x1, t) = (1*k22*(2*k1/(1 + k8*x3^k13) - 1)*k2/(1 + k7*x3^k12)*x1 + 1*k22*2*k4/(1 + k9*x3^k14)*x2*k5/(1 + k11*x1^k16)*(1 - k3/(1 + k10*x3^k15)))/k22,
  diff(x2, t) = (1*k22*2*k2/(1 + k7*x3^k12)*x1*(1 - k1/(1 + k8*x3^k13)) + 1*k22*(2*k3/(1 + k10*x3^k15) - 1)*k4/(1 + k9*x3^k14)*x2)/k22,
  diff(x3, t) = (1*k22*2*k4/(1 + k9*x3^k14)*x2*(1 - k3/(1 + k10*x3^k15))*(1 - k5/(1 + k11*x1^k16)) + (-1)*k22*k6*x3)/k22 }