I applied for citizenship in August and got receipt notice. The receipt date is 8/18/2010 and priority date is also 8/18/2010. When I checked the online status it says a RFE was mailed on September 3rd. I assume it's the FP notice. But I have not got any FP letter or any other letter from USCIS. Should I wait or call the USCIS? Please help.