Text 37 

vrsninam vasudevo ’smi
pandavanam dhananjayah
muninam apy aham vyasah
kavinam usana kavih

Translation

Of the descendants of Vrishni I am Vasudeva, and of the Pandavas I am Arjuna. Of the sages I am Vyasa, and among great thinkers I am Usana. 

Commentary by Srila Prabhupada 

Krishna is the original Supreme Personality of Godhead, and Baladeva is Krishna’s immediate expansion. Both Lord Krishna and Baladeva appeared as sons of Vasudeva, so both of Them may be called Vasudeva. From another point of view, because Krishna never leaves Vrindavana, all the forms of Krishna that appear elsewhere are His expansions. Vasudeva is Krishna’s immediate expansion, so Vasudeva is not different from Krishna. It is to be understood that the Vasudeva referred to in this verse of Bhagavad-gita is Baladeva, or Balarama, because He is the original source of all incarnations and thus He is the sole source of Vasudeva. The immediate expansions of the Lord are called svamsha (personal expansions), and there are also expansions called vibhinnamsha (separated expansions). 

Amongst the sons of Pandu, Arjuna is famous as Dhananjaya. He is the best of men and therefore represents Krishna. Among the munis, or learned men conversant in Vedic knowledge, Vyasa is the greatest because he explained Vedic knowledge in many different ways for the understanding of the common mass of people in this Age of Kali. And Vyasa is also known as an incarnation of Krishna; therefore Vyasa also represents Krishna. Kavis are those who are capable of thinking thoroughly on any subject matter. Among the kavis, Usana, Sukracarya, was the spiritual master of the demons; he was an extremely intelligent and far-seeing politician. Thus Sukracarya is another representative of the opulence of Krishna.

Commentary by Sri Visvanatha Cakravarti Thakur

Among the Vrsnis, I am Vasudeva, who is my father. He is my vibhuti. The rule is given as follows: prajnaditvat (Panini 5.4.38). Sometimes the long a can have the same meaning as short a. The long a is used to indicate self-interest. Others would propose that he should have said "Among the Vrsnis, I am myself, the son of Vasudeva." This however is not agreeable, as it does not mean anything.