The use of "sir" and "ma'am" as forms of address for superiors are common in the United States armed forces. U.S. Army and U.S. Air Force regulations state that "ma'am" is an appropriate greeting for junior personnel when rendering a hand salute to a female superior. The use of formal modes of address such as "sir" or "ma'am", ingrained in military culture, is distinct from the American corporate or civilian setting, where most co-workers refer to each other by first name and use of formal titles is considered awkward. A 2017 U.S. Army Human Resources Command publication noted that in the Northern United States, "it is common to hear young to middle-aged women say, 'Don't call me ma'am,' as it is seen as a title reserved for older women."