// Convenience to make things more legible in the following code
const float & x = some.buried.variable.elsewhere;

// Go on to use x in calculations...

assert(&x == &some.buried.variable.elsewhere)

const float x = some.buried.variable.elsewhere;

float &x = some.buried.variable.elsewhere;

float const &x = 3.0; // non-sense. don't use reference here

float const &x = get_some_float(); // non-sense too.

const T& x = some.buried.variable.elsewhere;