there is a good web site to ask questions like this, asktheref.com just pose the question and they will answer to you via email and post your question and answer on the web site.
I also agree that parents should refrain from yelling at the ref. for the most part they do not have any idea what the call is or how it should be made or the laws of the game for that matter. if they think they are so good at calling the game, take a class and do it from the center of the field. it is much more difficult to call a perfect game on the field while it is so easy to do so from the stands. as to the coach he should know when to stop.
