Possible Clues:

• 1972 missile pact
• First of two U.S./U.S.S.R. pacts
• '70s missile pact
• Nixon-Brezhnev missile pact
• Nixon and Brezhnev signed it in '72
• U.S./Soviet pact
• Pact signed by Nixon
• Missile pact of 1972
• 1970s pact partly negotiated in Helsinki
• Treaty signed by Nixon and Brezhnev