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

YANG, S. AND PRENTICE, R. L. (2011). Estimation of the 2-sample hazard ratio function using a semiparametric model. Biostatistics 12, 354-368.

YANG, S. AND PRENTICE, R. L. (2010). Improved Logrank-Type Tests for Survival Data Using Adaptive Weights. Biometrics 66, 30-38.

YANG, S. AND PRENTICE, R. L. (2005). Semiparametric analysis of short-term and long-term hazard ratios with two-sample survival data. Biometrika 92, 1-17.

YANG, S. AND 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}},
  }