December 1957 tornado outbreak sequence
{'<entity_0>': 'December 1957 tornado outbreak sequence', '<entity_1>': 'tornado outbreak sequence'}
[['December 1957 tornado outbreak sequence', 'instance of', 'tornado outbreak sequence']]
The <entity_0>, was a significant <entity_1> that affected the southern Midwest and the South of the contiguous United States on December 18–20, 1957.
['tornado outbreak sequence']