McGill University. Industrial Relations Centre, Pathy, A. C., & Loerick, G. (1979). The Problem of "essentia services": Inconvenience, importance, or emergency. Industrial Relations Centre.
توثيق أسلوب شيكاغو (الطبعة السابعة عشر)McGill University. Industrial Relations Centre, Alexander C. Pathy, و Glenna Loerick. The Problem of "Essentia Services": Inconvenience, Importance, or Emergency. Montreal: Industrial Relations Centre, 1979.
توثيق جمعية اللغة المعاصرة MLA (الإصدار التاسع)McGill University. Industrial Relations Centre, et al. The Problem of "Essentia Services": Inconvenience, Importance, or Emergency. Industrial Relations Centre, 1979.
تحذير: قد لا تكون هذه الاستشهادات دائما دقيقة بنسبة 100%.