Replace Invalid Link (#3297)
Replace Invalid Link (#3297)

The URL `https://homes.cs.washington.edu/~luheng/files/acl2017_hllz.pdf` is in the state of 404.
I replace it by the url from ACL Anthology `https://www.aclweb.org/anthology/P17-1044`.
allenai/allennlp,allenai/allennlp,allenai/allennlp,allenai/allennlp