There are many good resources for the identification of AIS. Here are two of the best:

University of Minnesota Invasive Species Identification Guide

Minnesota DNR AIS

You can always contact the Itasca AIS Program or the local DNR office for help identifying an AIS sample you have:

Itasca County AIS Hotline: 218-256-4243
DNR Northeast Region AIS Specialist: 218-328-8821