Barker, J. L. NEMA standards for traffic control systems. Traffic engineering : official publication of the Institute of Transportation Engineers.
توثيق أسلوب شيكاغو (الطبعة السابعة عشر)Barker, John L. "NEMA Standards for Traffic Control Systems." Traffic Engineering : Official Publication of the Institute of Transportation Engineers .
توثيق جمعية اللغة المعاصرة MLA (الإصدار التاسع)Barker, John L. "NEMA Standards for Traffic Control Systems." Traffic Engineering : Official Publication of the Institute of Transportation Engineers, .
تحذير: قد لا تكون هذه الاستشهادات دائما دقيقة بنسبة 100%.