The sound vibration omkara is the root of Vedic knowledge. This omkara is known as maha-vakya, or the supreme sound. Whatever meaning is in the supreme sound omkara is further understood in the Gayatri mantra. Again, this same meaning is explained in Srimad-Bhagavatam in the four slokas known as catuh-sloki, which begin with the words aham evasam evagre. The Lord says, "Only I existed before the creation." From this verse, four slokas have been composed, and these are known as the catuh-sloki. In this way the Supreme Personality of Godhead informed Lord Brahma about the purpose of the catuh-sloki. Again, Lord Brahma explained this to Narada Muni, and Narada Muni explained it to Srila Vyasadeva. This is the parampara system, the disciplic succession. The import of Vedic knowledge, the original word pranava, has been explained in Srimad-Bhagavatam. The conclusion is that the Brahma-sutra is explained in Srimad-Bhagavatam.