West Bengal Chief Minister Mamata Banerjee on Monday urged students and researchers to preserve history so that it is not changed due to different political ideology."I request students and researchers to make efforts to conserve our history and make sure it is not changed due to any political ideology," Banerjee said during her address at the convocation ceremony of Calcutta University here.Indirectly alluding to an atmosphere of divisiveness, she wished that the Lord must throw more light all around so that there is "no narrow-mindedness and all differences between people can be erased"."The freedom of various institutions should not be curbed. In Bengal, the land of great personalities like Swami Vivekananda, Rabindranath Tagore, Netaji Subhash Chandra Bose and others, we must uphold the concept of unity," she said.The university conferred honorary DLitt on former Governor Gopal Krishna Gandhi at its annual convocation ceremony.