Minimum staffing need data

Hi all, I am trying to find some peer review articles or any data on the safe minimum number of nurses in an ER. My ER is a 22 bed level 3 trauma center with an average census of 80-100 per day. We have no policy stating the minimum number of nurses needed to be present at all times, and as charge, I'm pressured every day by administration to put nurses on call. I feel ok with 3-4 nurses (including myself) at all times, but they are wanting me to work with less (when I started, we had 5 nurses and 2 techs at all times) most of the time we no longer have a tech and are working with less than 4 (including myself) I'd like to present my director with some evidence to suggest what is safe. I'd also like to know what you guys are working with and consider safe even if you don't have a peer reviewed article or statistics thanks!