@article{Urbanowski:2004,
  author  = "K. Urbanowski",
  title   = "Need the masses of unstable particles and their antiparticles be equal in the CPT-invariant system",
  journal = "Modern Physics Letters A",
  volume  = "Vol. 19",
  number  = "no 7",
  pages   = "481--496",
  year    = "2004",
}