I recently purchased my first Catechism of the Catholic Church Second Edition, to help further my studies on the Word of God. As I scan through the pages I see several different types of citations shown at the bottom of the pages. Many are reference Holy Scripture, but many others appear to referencing other sources. I presume many of these are Councils and other official Church declarations.
I was not able to find an explanation of each of these sources in the book, perhaps I overlooked it? Does anyone have a link to a summary of these sources, or can you help explain this for me?