Advanced General Relativity - Lecture 21

          @misc{ scivideos_PIRSA:13040001,
            doi = {},
            url = {https://pirsa.org/13040001},
            author = {Sorkin, Rafael},
            keywords = {},
            language = {en},
            title = {Advanced General Relativity - Lecture 21},
            publisher = {Perimeter Institute for Theoretical Physics},
            year = {2013},
            month = {apr},
            note = {PIRSA:13040001 see, \url{https://scivideos.org/pirsa/13040001}}
          }