This is a copy of the Multi-News dataset, except the input source documents of its test split have been replaced by a sparse retriever. The retrieval pipeline used:

• query : The summary field of each example
• corpus : The union of all documents in the train , validation and test splits
• retriever : BM25 via PyTerrier with default settings
• top-k strategy : "oracle" , i.e. the number of documents retrieved, k , is set as the original number of input documents for each example

Retrieval results on the test set: