> a = 10, b = 28, c = 8/3,
```
def lorenz_I(a, b, c):
h = lambda x, y: sqrt(x*x + y*y)
return lambda x, y, z:(
(-a - 1)*x + (a - b)*y + (1 - a)*h(x, y) + y*z,
(b - a)*x - (a + 1)*y + (b + a)*h(x, y) - (x + h(x, y))*z,
y/2 - c*z
)
```
## References
> Lorenz-Attraktor
> http://page.math.tu-berlin.de/~gunn/Files/mvws13html/html2420/lorenz2420.html
>
> R. Miranda & E. Stone, The proto-Lorenz system, Physics Letters A 178 (1993) 105-113.