With no explanation, label text_A→text_B with either "not_related" or "related".
text_A: Boeing 737s serve markets previously filled by other midsize airliners.
text_B: The 231st Brigade was an infantry brigade of the British Army that saw active service in both World War I and World War II .. Brigade. Brigade. World War I. World War I. World War II. World War II. infantry. infantry. brigade. brigade. British Army. British Army. In each case it was formed by redesignation of existing formations .. In the World War I it fought in Palestine and on the Western Front , while in World War II it served in the Allied invasion of Sicily , Italy and the Normandy landings of 6 June 1944 .. World War I. World War I. World War II. World War II. Palestine. Sinai and Palestine Campaign. Western Front. Western Front ( World War I ). Allied invasion of Sicily. Allied invasion of Sicily. Italy. Allied invasion of Italy. Normandy landings of 6 June 1944. Normandy landings
not_related.