Aliens — Refugees — Refugee status — Geneva Convention Relating to the Status of Refugees, 1951, and Protocol, 1967 — Claim for asylum and prohibition of deportation based upon membership of a “particular social group” — Whether a cognizable “social group” — UNHCR Handbook on Procedures and Criteria for Determining Refugee Status — Guidance from — “Clear probability” of persecution and “well-founded fear” of persecution — Immigration and Nationality Act 1952 — Refugee Act 1980 — The law of the United States