{ diff(x1, t) = (1*k3*(1 + k4*x3^4/(k5^4 + x3^4))*x1^2/(x1^2 + k7/(1 + x3^4/k6^4)) + (-1)*k10*x1 + 1*k11)/k8,
  diff(x2, t) = (1*k15*x3^k17/(k16^k17 + x3^k17) + (-1)*k18*x2^k21/(k19^k21 + x2^k21)*x3^k22/(k20^k22 + x3^k22) + (-1)*k23*x2)/k9,
  diff(x3, t) = (1*k12 + 1*k13*k14 + (-1)*k15*x3^k17/(k16^k17 + x3^k17) + 1*k18*x2^k21/(k19^k21 + x2^k21)*x3^k22/(k20^k22 + x3^k22) + 1*k23*x2 + (-1)*k24*x3)/k8 }