I'e worked on an REU research project which I'd like to get a LOR from, and I'm slightly unsure as to the etiquette of the inquiry. Nearly all my work was managed and supervised by a post doc since the senior scientist was traveling for the majority of my stay at the lab (even then, I only met her three times). The post doc clearly knows my work better, and from previous posts I;ve gathered that it's better to have the post doc write the letter and have the professor/lead scientist co-sign it. However, is it a better idea to contact the professor asking for a letter written by a post doc, or contact a postdoc and then ask if they can have the professor cosign? In essence, I'm not sure whether it is advisable to contact the professor or post doc at first. I don't want to slight the postdoc or the professor by leaving them out.