To cite the R package 'YPmodel' in publications use:

YANG S, Prentice R (2011). “Estimation of the 2-sample hazard ratio function using a semiparametric model.” Biostatistics, 12(2).

YANG S, Prentice R (2010). “Improved Logrank-Type Tests for Survival Data Using Adaptive Weights.” Biometrics, 66(1).

YANG S, Prentice R (2005). “Semiparametric analysis of short-term and long-term hazard ratios with two-sample survival data.” Biometrika, 92(1).

YANG S, ZHAO Y (2012). “Checking the Short-Term and Long-Term Hazard Ratio Model for Survival Data.” Scandinavian Journal of Statistics.

GASTROINTESTINAL TUMOR STUDY GROUP (1982). “A comparison of combination chemotherapy and combined modality therapy for locally advanced gastric carcinoma.” Cancer.

Corresponding BibTeX entries:

  @Article{,
    title = {Estimation of the 2-sample hazard ratio function using a
      semiparametric model},
    journal = {Biostatistics},
    volume = {12},
    number = {2},
    year = {2011},
    author = {Song YANG and ROSS L. Prentice},
  }

  @Article{,
    title = {Improved Logrank-Type Tests for Survival Data Using
      Adaptive Weights},
    journal = {Biometrics},
    volume = {66},
    number = {1},
    year = {2010},
    author = {Song YANG and ROSS L. Prentice},
  }

  @Article{,
    title = {Semiparametric analysis of short-term and long-term hazard
      ratios with two-sample survival data},
    journal = {Biometrika},
    volume = {92},
    number = {1},
    year = {2005},
    author = {Song YANG and ROSS L. Prentice},
  }

  @Article{,
    title = {Checking the Short-Term and Long-Term Hazard Ratio Model
      for Survival Data},
    journal = {Scandinavian Journal of Statistics},
    year = {2012},
    author = {Song YANG and Yichuan ZHAO},
  }

  @Article{,
    title = {A comparison of combination chemotherapy and combined
      modality therapy for locally advanced gastric carcinoma},
    journal = {Cancer},
    year = {1982},
    author = {{GASTROINTESTINAL TUMOR STUDY GROUP}},
  }