There is a good site that gives lots of detail about this subject.
The site is here: http://www.maxwells-equations.com/index.php#maxwells
It’s clickable to all the symbol explanations.
I wanted to request permission to post this, but I couldn’t find an email address on the website.
I’ve updated my RC Response document (See the Math Documents link from the main menu). I added a section that explains why time shifting involve subtracting rather than adding slices of time.
Here’s another page that goes into even more detail.
Source: SIGNALS, EXCITATION, and RESPONSE