https://s0.wp.com/latex.php?latex=%5Cdisplaystyle++%5Csum_%7Bi%3D1%7D%5E%5Cinfty+%7C%5Cmu%28%5CDelta_i%29%7C%5Cleq+%5C%7C%5Cmu%5C%7C_%7Bba%7D.+&bg=ffffff&fg=000000&s=0