{Documentary) History of the Church Referred to in the old D&C Section Headings

Each of the sections of the OLD hard copy Doctrine and Covenants (my hard copy gives a publication date of 1981/2005) begins with a new (at that time) section heading which gives the historical background, or context, of how, where, when, etc. that  revelation was received.  Each old section heading also references the History of the Church, meaning the Documentary History compiled from journals and letters of Joseph Smith, usually written down by one of his scribes or friends.  For example, the old heading of D&C section 4 says: 

"Revelation given through Joseph Smith, the Prophet, to his father, Joseph Smith, Sen., at Harmony, Pennsylvania, February 1829, HC 1:28"  

The NEW, digital versions of the headings LEAVE OUT  the references to the HC.  The new, digital version says, 

"SECTION 4

Revelation given through Joseph Smith the Prophet to his father, Joseph Smith Sr., at Harmony, Pennsylvania, February 1829." 

So, don't get rid of your old, printed out hard copy scriptures: that version is very helpful for scripture study!

Of course, you can read MORE and more accurate background/context at the Joseph Smith Papers website. Especially helpful is the  Joseph Smith’s Revelations: A Doctrine and Covenants Study Companion from the Joseph Smith Papers. 

But for 100 years, the History of the Church was the "go to" source for historical information. If you do not own a set of these volumes of the (Documentary) History of the Church, they are available FREE online at BYU Studies (again, thank you, John Welch).

https://byustudies.byu.edu/further-study/history-of-the-church/