Harpen, N. H. v., & Watkins, S. J. (1930). The electrometric determination of the hydrogen ion concentration in the latex of Hevea brasiliensis and its applicability to technical problems. Varekamp & Co.
توثيق أسلوب شيكاغو (الطبعة السابعة عشر)Harpen, Nicolaas Hendrik van, و S. J. Watkins. The Electrometric Determination of the Hydrogen Ion Concentration in the Latex of Hevea Brasiliensis and Its Applicability to Technical Problems. Medan: Varekamp & Co, 1930.
توثيق جمعية اللغة المعاصرة MLA (الطبعة الثامنة)Harpen, Nicolaas Hendrik van, و S. J. Watkins. The Electrometric Determination of the Hydrogen Ion Concentration in the Latex of Hevea Brasiliensis and Its Applicability to Technical Problems. Varekamp & Co, 1930.
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