Не магу настроить ЧПУ для страниц

/supplier.php?id_supplier=16
/supplier.php?id_supplier=17
/authentication.php?back=order.php?step=1
/authentication.php?back=my-account.php
/authentication.php?back=my-account.php
/authentication.php?back=identity.php
/authentication.php?back=addresses.php
/authentication.php?back=history.php

RewriteRule ^authentication$ /authentication.php [QSA,L]
RewriteRule ^([0-9]+)__([a-zA-Z0-9-]*) /supplier.php?id_supplier=$1$3 [QSA,L,E]
RewriteRule ^([0-9]+)__([a-zA-Z0-9-]*) /authentication.php?back=$1 [QSA,L,E]

что тут не так ?? помогите !!!!!