@conference{4983,
  author = {B. Stern and Marek Sikora and R. Svensson},
  title = {Pair cascades triggered by relativistic protons in AGNs},
  year = {1992},
  publisher = {AIP},
  address = {College Park, Maryland (USA)},
  url = {http://link.aip.org/link/APCPCS/v254/i1/p313/s1\&Agg=doi},
  doi = {10.1063/1.42202},
}