SAP BASIS Book

This will give you the user who has released the request not who imported the request. To know who has imported the request:
Go to SE 16, give table TPLOG in CMDSTRING enter request number and then execute. This will give name of importer.
I am not sure if this works at your end. But it works at my end please try it. Try the following steps:
1. TA SE16.
2. Enter table E070.
3. Enter the Request you want to check for and execute.
4. Check the column AS4USER - he is the one who has released the request
How can I check who has imported a transport request?