CREATE TABLE table_203_109 (id DECIMAL, "treaty" TEXT, "organization" TEXT, "introduced" DECIMAL, "signed" DECIMAL, "ratified" DECIMAL)

which was the first human rights treaty to be signed ?
SELECT "treaty" FROM table_203_109 ORDER BY "signed" LIMIT 1
SELECT "treaty" FROM "table_203_109" ORDER BY "signed" NULLS FIRST LIMIT 1