They didn't release them on the data sheet for the 4351 you will have to check with TAC they may be able to find out internally , doesn't look like they were released for a lot of 4000 series routers for some reason
http://www.cisco.com/c/en/us/products/collateral/routers/4000-series-integrated-services-routers-isr/datasheet-c78-732542.html
