  We have shown that the Born rule $(\rho=|\psi|^{2})$ is inconsistent with
Lorentz symmetry of the Salpeter equation (square root Klein-Gordon equation).
So we find relativistic modification of the Born rule as
$\rho=\frac{1}{2mc^{2}}(|\sqrt{\widehat{H}-mc^{2}}\psi|^{2}+|\sqrt{\widehat{H}+mc^{2}}\psi|^{2})$
, which is consistent with Lorentz symmetry of this equation
