Shri Shri Sarveshvara Bhagavan (centre) being worshipped by Shri Nimbarkacharya (right), his successor Shri Shrinivasa (left top) and his other disciple Shri Audumbaracharya (left bottom) on the banks of the Yamuna in Shri Vrindavana Dham. (Taken from the Radha Nimbarkavihari Mandira at Nimba Grama)
The Nimbarka Sampradaya also known as the Hamsa Sampradaya.
Hamsa Sampradaya is one of the four authorised Vaisnava Sampradayas (philosophical schools characterised by leaders in disciplic succession) as according to the Padma Puran, one of the eighteen main Puran. The verse says:
sampradāyavihīnā ye mantrāste niṣphalā matāḥ|
ataḥ kalau bhaviśyanti catvāraḥ sampradāyinaḥ||
Śrī-brahmā-rudra-sanakā vaiṣṇavā kṣitipāvanāḥ|
catvāraste kalau bhāvya hyutkale puruṣottamāt||
rāmānujaṃ śrī svicakre madhvācaryaṃ caturmukhaḥ|
śrīviṣṇusvāminaṃ rudro nimbādityaṃ catuḥsanāḥ||
ll mantras which have been given (to disciples) not in an authorised Sampradaya are fruitless. Therefore, in Kali Yuga, there will be four bona-fide Sampradayas. Each of them were ignaugurated by Shri Devi and known as the Shri Sampradaya, Lord Brahma and known as the Brahma Sampradaya,Lord Rudra and known as the Rudra Sampradaya; and the Four Kumaras and known as Sanakadi Sampradaya. Shri Devi made Ramanujacarya the head of that lineage. So too Lord Brahma appointed Madhvacarya, Lord Rudra appointed Vishnuswami and the four Kumaras chose Nimbaditya (an epithet for Shri Nimbarkacarya).
As seen from the above verses in the Padma Puran, the four Sampradayas are at least documented, though the date of this quotation is questionable. According to the literature available through the Shri Nimbarka Sampradaya and documents from other sources (such as the Bhaktamala by Nabhadasa) of the Vaisnava community.
Yugal Maha Mantra
Radhe Krishna Radhe Krishna Krishna Krishna Radhe Radhe
Radhe Shyam Radhe Shyam Shyam Shyam Radhe Radhe
राधे कृष्ण राधे कृष्ण , कृष्ण कृष्ण राधे राधे।
राधे श्याम राधे श्याम, श्याम श्याम राधे राधे ।।