James Hamilton and Christopher Schroeder's (1994) article on agency behavior shed light on the issue of whether agency rulemaking may be "ossifying." Certain types of agency rules are much more likely to be accompanied by at least one guidance document.
Jeffrey S. Lubbers,
Anatomy of a Regulatory Program: Comment on “Strategic Regulators and the Choice of Rulemaking Procedures”,
57 Law and Contemporary Problems
Available at: http://scholarship.law.duke.edu/lcp/vol57/iss2/6