These articles address the various reasons groups seek to use Article V to propose a Constitutional provision preventing multiple-subject Congressional bills, unrelated amendments, and “(whatever the name is for pork barrel add-ons)”:
Uneasy Riders: The Case for a Truth-in-Legislation Amendment
– This paper by Brannon P. Denning and Brooks R. Smith, published in 1999 in the Utah Law Review, refers to a Single-Subject Amendment as a Truth-in-Legislation Amendment (TILA), and suggests that it would be modeled on provisions found in most state constitutions.
The Truth-in-Legislation Amendment: An Idea Whose Time Has Come
– A subsequent paper on this same topic, by Brandon P. Denning and Brooks R. Smith published in the 2011 Tennessee Law Review.