I am looking for these articles:
1) pH‐Measurements in alcohol‐water mixtures, using aqueous standard buffer solutions for calibration, W. J. Gelsema, C. L. de Ligny, A. G. Remijnse, Miss H. A. Blijleven, Volume 85, Issue 7, 1966
2) pH‐measurements in alcohol‐water mixtures. On the use of aqueous standard buffer solutions for calibration, W. J. Gelsema, C. L. de Ligny, Miss H. A. Blijleven, Volume 86, Issue 8, 1967, Pages 852-864