Campbell, C. C. (1978). Ellipsis of do and did in inverted yes/no questions by native and non- native speakers.
توثيق أسلوب شيكاغو (الطبعة السابعة عشر)Campbell, Cherry Colleen. Ellipsis of Do and Did in Inverted Yes/no Questions by Native and Non- Native Speakers. 1978.
توثيق جمعية اللغة المعاصرة MLA (الطبعة الثامنة)Campbell, Cherry Colleen. Ellipsis of Do and Did in Inverted Yes/no Questions by Native and Non- Native Speakers. 1978.
تحذير: قد لا تكون هذه الاستشهادات دائما دقيقة بنسبة 100%.