The above approach to decimal expansions, including the proof that 0.999... = 1, closely follows Griffiths & Hilton's 1970 work A comprehensive textbook of classical mathematics: A contemporary interpretation.
التقريب للتوسع العُشري أعلاه المتضمن لإثبات 1 =...0.999، يستند لعمل Griffiths و Hilton المنشور عام 1970 تحت اسم "comprehensive textbook of classical mathematics: A contemporary interpretation".