Previously you answered my question about may my supervisor write the cover letter for me if I want file my NIW I-140 as self-petition. But I think probably I did not make it clearly. Would you please tell me if I can fill the I-140 form by my self as self-petition and let my supervisor (I'm a postdoc), not the university, write the cover letter for me in a manner such as "I am supervisor of Dr. XXX, for such such reason, I respectly request you approve Dr. xxx's petition"? If you think it is OK, do you think I still have the freedom to change the employer during the processing(just like a regular self-petition NIWer)? Because this realy makes me confuse, hopefully I can get some suggestions here. If anyone can give me the suggestion, it would be great appreciated. Thanks.