Formal.
As far as I know, there is no such thing as either standard or practiced diction. Informal is the way you communicate with your friends, for instance, which is not how you would write a thesis paper, legal document, etc.
Dickens, Charles. Great Expectations. New York: Dodd, Mead, 1942. Print.
Structure: Last, First M. Book. City: Publisher, Year Published. Print.
I think it's cultural details maybe I'm right or not.
