I have noticed lately that when citing Church documents some writers are perhaps less than clear about the use of capitalization.
Here is a small point for students and writers to take into consideration.
A common "mistake" rests in simply capitalizing all the words of the title of a document, itself usually taken from the first few words of the document. I write "mistake", though that word is too strong. It is so common to capitalize all the words as to be acceptable. You find this even on the Holy See’s website collections of documents.
But… if you want to be perhaps more precise, you could capitalize only what ought to be.
You will often see Lumen Gentium for the Council’s document on the Church. That’s fine, I guess. But more correctly it could be written as Lumen gentium, because that is how the document begins. So too for Gaudium et spes or an encyclical such as Humanae vitae.
On the other hand we should write Sacrosanctum Concilium, not Sacrosanctum concilium, because the word Concilium ought to be capitalized on its own merit.
The same goes for the encyclicals Mystici Corporis Christi or Divino afflante Spiritu or the Motu Proprio (or motu proprio, etc.) Summorum Pontificum…. not Summorum pontificum.
If you are going to chose one convention or another, be consistent. Also, if you are going to go with the more correct way, double check to make sure you are in fact capitalizing what needs to be capitalized.
A small point.