What follows is an opinion from a United States Court of Appeals.
Your task is to identify the most frequently cited federal rule of civil procedure in the headnotes to this case. Answer "0" if no federal rules of civil procedure are cited. For ties, code the first rule cited.

COMMISSIONER OF INTERNAL REVENUE, Petitioner, v. SHERWOOD SWAN AND COMPANY, Ltd., et al., Respondents.
No. 19627.
United States Court of Appeals Ninth Circuit.
Nov. 8, 1965.
Louis F. Oberdorfer, Asst. Atty. Gen., Lee A. Jackson, Harry Baum, Edward L. Rogers, Attys., Dept, of Justice, Washington, D. C., for petitioner.
James F. Crafts, Jr., Orrick, Dahlquist, Herrington & Sutcliffe, San Francisco, Cal., for respondent.
Before HAMLEY, HAMLIN and DUNIWAY, Circuit Judges.
HAMLEY and DUNIWAY,
Circuit Judges:
The decision of The Tax Court is affirmed for the reasons stated by that court in its opinion reported at 42 T.C. 299.

Question: What is the most frequently cited federal rule of civil procedure in the headnotes to this case? Answer with a number.

Answer: