# How to update package?

when I use << PhysicalConstants` I get the message like :General::obspkg: PhysicalConstants is outdated... see the Compatibility Guide for more infomation... The question is how to update it? My version is MA9.0.

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For those who would still prefer to work with the old style of units, but with many added features, I still sell the ExtendUnits package from my web site. It still has the old PhysicalConstants built in. –  David Park Nov 16 '13 at 4:43