Let's go over how you would read case citations:
Let's look at the first one here:
Roe v. Wade, 410 U.S. 113 (1973)
Right away we can determine it's a US Supreme Court decision. How?
From the US abbreviation leading us to the US Reports reporter. Then you have the case name at the beginning, the volume number, page number and the year.
In the second example you really have no good way to know where to find this without going to an abbreviation guide to determine that the abbreviation P2d refers to the Pacific Reports regional reporter.
The Bluebook by 
Prince's Bieber Dictionary of Legal Abbreviations by Here are some snapshots of what those look like. as you can see these are guides to not just statute citation abbreviations but also include abbreviations to different courts and case reporters, secondary sources such as law reviews, legal encyclopedias, codes of regulations, etc. So, these are really handy to have around for when a patron comes to the desk and asks for help locating a legal citation of nearly any sort.
