Explanation:

The literary works and their authors mentioned have been significant in ancient Indian history:

Devichandragupta - This work is indeed attributed to Bilhana, a renowned 11th-century Kashmiri poet. Therefore, the first pair is correctly matched.

Hammira Mahakavya - This is a work by Nayachandra Suri, a Jain monk and scholar who lived in the 12th century. It is an epic poem about the life of the Chahamana king Hammira, making the second pair correct.

Milinda Panha - This is a Buddhist text which documents the dialogues between the Indo-Greek king, Menander I (Milinda in Pali), and the Buddhist monk Nagasena. Nagarjuna is a celebrated Buddhist philosopher but is not associated with the Milinda Panha, so the third pair is incorrect.

Nitivakyamrita - This is a work by Somadeva Suri, a Jain monk and scholar of the 10th century, known for his writings on ethics and morality. So, the fourth pair is also correctly matched.

With two pairs correctly matched (1 and 2)