Vaishnava Samhita. Katha Sangraham. Vol III Book VI Chp 25 Shlokas 4 & 5

तृतीये व्यासदासस्य प्रार्थनां नन्दनन्दनः |
अङ्गीकृत्य दधाराशु मुरलीं स्वयमेव हि ||
चतुर्थे कीर्तिता व्यक्तं गङ्गायमुनायोःकथा |
राधावल्लभकिङ्कर्योर्गोपॆभावविमुग्धयोः ||

Chapter Three describes the exciting incident of Shri Nandakumara paying heed to the prayers of Vyasadeva and voluntarily taking in the hand the flute offered to Him. The Fourth Chapter narrates the story of Ganga and Yamuna who were the devotees of Shri Radhavallabha and who were full of Gopi prem.