The stress energy momentum tensor of the Einstein field equations contains multiple density terms such as the energy density and the momentum density. I know how to calculate relativistic energy and momentum, but none of the websites or videos that I have watched make mention of any division of these relativistic terms by volume. Now I may be taking the word density too literally, but when I hear the word density I define it as the amount of something (usually mass or energy) divided by the volume in which that thing is contained. Having said that, I must ask you all this question: Am I supposed to divide the relativistic quantities by some measure of volume to derive these various density terms? I am just asking this because nothing that I have seen makes any mention of volume when talking about the density terms in the stress energy momentum tensor. If I do have to divide by volume, do I have to divide by any new volumes that are brought on by Lorentz contraction of special relativity, or do I simply divide by the object's ordinary volume? Finally, are the 1st row of elements and the 1st column (aside from T00) really the same quantities? I ask this because some sources describe the first row as the energy flux and the 1st column as the momentum density. Other sources describe both the 1st row and the 1st column as momentum density. Sorry if these questions seem to basic. I am in high school right now and my school sadly does not have a class on general relativity. Most of my knowledge in this field comes due to self study. It is for this reason that I would greatly appreciate it if anyone posted a link to a free downloadable paper, pdf or university textbook pertaining to this area. Don't worry about finding a simplified version because I am well versed in the mathematics of it. Thank you.