The problem is even worse when the source sentences get longer and more complicated.
the results show that: (1) although the candidate paraphrases acquired by Mt engines are noisy, they provide good raw materials for further paraphrase generation; (2) the selection-based technique is effective, which results in the best performance; (3) the decodingbased technique is promising, which can generate paraphrases that are different from the candidates; (4) both the selection-based and decoding-based techniques outperform a state-of-the-art approach SPG (Zhao et al., 2009).