كتاب الْمَسَاجِدِ وَمَوَاضِعِ الصَّلاَةِ
5  
The Book of Mosques and Places of Prayer
(30)
Chapter: The one who catches up with a rak`ah of the prayer, he has caught up with that prayer
(30)
باب مَنْ أَدْرَكَ رَكْعَةً مِنَ الصَّلاَةِ فَقَدْ أَدْرَكَ تِلْكَ الصَّلاَةَ ‏
Sahih Muslim 608 d

This hadith has been reported by Ma'mar with another chain of transmitters.

وَحَدَّثَنَاهُ عَبْدُ الأَعْلَى بْنُ حَمَّادٍ، حَدَّثَنَا مُعْتَمِرٌ، قَالَ سَمِعْتُ مَعْمَرًا، بِهَذَا الإِسْنَادِ ‏.‏
Reference : Sahih Muslim 608d
In-book reference : Book 5, Hadith 212
USC-MSA web (English) reference : Book 4, Hadith 1267
  (deprecated numbering scheme)