proof_by_contradiction:
lr2011.07.15-0003
proof_by_contradiction:
lr2011.07.15-0004
proof_by_contradiction:
lr2011.07.15-0018
proof_by_contradiction:
lr2011.07.15-0038
proof_by_contradiction:
lr2011.07.15-0044
proof_by_contradiction:
lr2011.07.15-0054
proof_by_contradiction:
lr2011.07.15-0062
proof_by_contradiction:
lr2011.07.15-0137
proof_by_contradiction:
lr2011.07.15-0173
proof_by_contradiction:
lr2011.07.15-0188