My husband has been diagnosed with Stage 4-Squamous Cell Lung Cancer in which the left bronchus is blocked due to this cancer. He served during the Viet Nam era in Thailand, Ubon RAFB beginning in November 1966 through November 1967. His job was Cryogenic Fluids, making oxygen for the planes that flew missions to Viet Nam. He worked near the perimeter. We have filed a claim with VA for benefits and are being asked for factual information. Not sure what they are asking for. Can you help?