[Boost-users] newbie question: unordered map missing?

Hello, I'm poking around in the library for something like a hashmap and I found this file: http://www.boost.org/doc/libs/1_35_0/boost/interprocess/indexes/unordered_ma... (boost/interprocess/indexes/unordered_map_index.hpp) which includes this: #include which doesn't exist. Where can I find this file? Thank you -Julie