to rely on rules in reaching their decisions rather than adjudicate, where the promulgation of the rules is within the agency's statutory authority, and the rules themselves are not arbitrary or capricious. Heckler v. Campbell, . Agencies must abide by their own rules and regulations. Accardi v. Shaughnessy, . Courts must defer to administrative agency interpretations of the authority granted to them by Congress (1) where the intent of Congress was ambiguous and (2) where the interpretation was reasonable or permissible. Chevron U.S.A., Inc. v. Natural Resources Defense Council, Inc., . Chevron is probably the most frequently cited case in American administrative law. Type of rulemaking There are five levels of rulemaking procedure: Formal rulemaking, which is rulemaking for which the organic statute requires that rules be "made on the record after opportunity for an agency hearing" (that is, a trial-type hearing that is taken down by a transcriptionist into the record and for which the APA prescribes particular procedures). The phrase "on the record" is required to trigger requirements for formal rulemaking; simply requiring that rules be made "after a hearing" does not trigger the requirements of formal rulemaking. Informal rulemaking, also known as "notice-and-comment rulemaking", which is rulemaking for which no procedural requirements are prescribed in the organic statute, and for which the APA requires only notice and comment. Hybrid rulemaking, which is rulemaking for which particular procedural requirements beyond notice and comment are prescribed, but does not rise to the level of formal rulemaking. Negotiated rulemaking under 5 U.S.C. §§ 561–570 of the Administrative Procedure Act. Publication rulemaking, or "nonlegislative rulemaking", typically for procedural rules, interpretative rules, or matters relating to agency management or personnel, that an agency may promulgate by publication in the Federal Register. Nonlegislative rules: interpretative rules, "statements of policy" and guidance "Nonlegislative rules" include three main classes: interpretative rules under 5 U.S.C. § 553(b)(A), which interpret ambiguities in binding rules, but themselves have only the limited binding effect of Skidmore deference. "statements of general policy", purely hortatory rules directed to the public, also promulgated under 5 U.S.C. § 553(b)(A). Typically, a "statement of policy" uses words like "should" instead of "must" or "shall", to advise the public of an agency's preference that the agency does not intend to enforce. "housekeeping rules" or "matters relating to agency management or personnel" directed to agency staff, including agency staff manuals, staff instructions and memoranda, and the