20 C.F.R. § 216.64 What is required for payment.
Title 20 - Employees' Benefits
An eligible widow(er), surviving divorced spouse, or remarried widow(er) must: (a) Apply to be entitled for an annuity; and (b) Submit evidence requested by the Board to support his or her application.
Title 20: Employees' Benefits
PART 216—ELIGIBILITY FOR AN ANNUITY
Subpart G—Widow(er), Surviving Divorced Spouse, and Remarried Widow(er) Annuities
§ 216.64 What is required for payment.

