{ diff(x1, t) = (1*k28*k1*x1*(1 - x1/k10) + (-1)*k28*k5*x1 + (-1)*k28*k16*x3*x1)/k28,
  diff(x2, t) = (1*k28*k2*x2*(1 - x2/k11) + (-1)*k28*k6*x2 + (-1)*k28*k15*x3*x2)/k28,
  diff(x3, t) = (1*k28*k3*x5*x3*(1 - x3/k12) + (-1)*k28*k7*x3 + (-1)*k28*k17*x1*x3)/k28,
  diff(x4, t) = (1*k28*k15*x3*x2 + (-1)*k28*k8*x4 + (-1)*k28*k14*x4)/k28,
  diff(x5, t) = (1*k28*k14*x4 + 1*k28*k4*x3*x5*(1 - x5/k13) + (-1)*k28*k9*x5)/k28 }