  We propose Dual-CES -- a novel unsupervised, query-focused, multi-document
extractive summarizer. Dual-CES is designed to better handle the tradeoff
between saliency and focus in summarization. To this end, Dual-CES employs a
two-step dual-cascade optimization approach with saliency-based pseudo-feedback
distillation. Overall, Dual-CES significantly outperforms all other
state-of-the-art unsupervised alternatives. Dual-CES is even shown to be able
to outperform strong supervised summarizers.
