1. T. Kojita, C. Maccaferri, T. Masuda, M. Schnabl
    Topological defects in open string field theory
    Journal of High Energy Physics 1804 (2018) 057(01)-057(56).
  2. N. Mertes, M. Schnabl
    String field representation of the Virasoro algebra
    Journal of High Energy Physics 1612 (2016) 151(0)-151(13).