@article{Niinuma:2016mk,
  author = "Niinuma, Kotaro  and  Kino, Motoki  and  Doi, Akihiro  and  Isobe, Naoki  and  Koyama, Shoko",
  title = "{VLBI follow-up observations for the large X-ray flares of Mrk 421}",
  doi = "10.22323/1.178.0101",
  journal = "PoS",
  year = 2016,
  volume = "11th EVN Symposium",
  pages = "101"
}