(1) See A4 paper.
(2) An ARM-based system-on-chip (SoC) used in Apple mobile devices including the iPhone 4, 1st-generation iPad and 4th-generation iPod touch.
"A4." YourDictionary, n.d. Web. 17 August 2018. <http://www.yourdictionary.com/a4>.
A4. (n.d.). Retrieved August 17th, 2018, from http://www.yourdictionary.com/a4