Explanation: Apart from these poems, the first two books of the Tolkappiyam (a book on Tamil grammar and poetics written by Tolkappiyar) are also a part of the corpus of Sangam Literature.

• There is also mention of the Agattiyam, which was the first known book on Tamil grammar.
• It was supposedly written by the sage Agathiyar, and is believed to be lost beyond redemption.

Source: Tamil Nadu NCERT