Susan Addington (25 August 2016). "Modular Arithmetic". คลังข้อมูลเก่าเก็บจากแหล่งเดิมเมื่อ 4 July 2008. สืบค้นเมื่อ 28 November 2008.
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"Time". The New Encyclopædia Britannica. Vol. 28. 1986. pp. 660 2a. "Time". Encyclopædia Britannica. Encyclopædia Britannica Online Library Edition. สืบค้นเมื่อ 20 November 2013. (ต้องรับบริการ) "The use of AM or PM to designate either noon or midnight can cause ambiguity. To designate noon, either the word noon or 1200 or 12 M should be used. To designate midnight without causing ambiguity, the two dates between which it falls should be given unless the 24-hour notation is used. Thus, midnight may be written: May 15–16 or 2400 May 15 or 0000 May 16."