Yoga 
The authoritative scriptures on the science of Yoga are Patanjali's Yoga Sutras; Hatha Yoga Pradipika by Swami Swatmarama; Shiva samhita; Gheranda samhita and Goraksha samhita. 

Tantras  
Tantric scriptures are also called as ‘Agamas'- revelations. They are also based on the Vedas. Their authorship is credited to Lord Shiva who gave them to His consort Parvati. The Tantric scriptures are divided into three main groups according to the Deity chosen for worship. There are Vaishnava agamas or Pancharatra; the Shaiva agamas; and the Shakta agamas. The Tantras are broadly divided into three parts. Sadhana which includes spiritual practices and ritualistic forms of worship; Siddhi or powers accruing from these practices and the Philosophy. The tantras have elaborate rituals and symbols for those who needed them and supplied most of the temple rituals of India. The well known Tantric scriptures are Mahanirvana Tantra, Kularnava Tantra, Rudrayamala Tantra and Shat-Chakra Nirupana.

Background story of Bhagvad Gita

As a background for the Bhagavad Gita teaching, the lengthy story of the highly symbolic Mahabharata epic in which the Krishna-Arjuna discourse is set, need not be recounted in full. But a brief summation touching upon some of the principal characters and events will provide a basis to show author Vyasa's allegorical intent. The war setting of the Bhagavad Gita is an allegory. Nevertheless, the war story is also partly historical and can be taken as factual and lessons learnt so as to know how to deal with social or national conflicts. 

Ancient India was divided into many big and small kingdoms. Dhritarashtra was the acting king of a big kingdom whose capital was present Delhi. He was acting as a king on behalf of his younger brother Pandu who had become the king because Dhritarashtra being blind was not considered qualified to be the king. When king Pandu died early and his children had not yet grown up to take over the kingship Dhritarashtra was acting on his behalf. Gandhari was a young girl whose marriage was arranged with Dhritarashtra. She protested against this marriage but she was told by her parents that this marriage was coming upon her forced by destiny and they are helpless. When she realized the truth of this fact, she not only accepted her destiny gracefully but decided to share the pain of her blind husband and so blind folded herself for life. In due time she gave birth to hundred children the eldest of whom was Duryodhana the villain in this story. Gandhari is a great and respected lady in Indian culture. She realized soon after marriage that her husband carries a grievance against destiny and is very jealous and ambitious. She did her best duty as a wife to make the husband accept his destiny and not to be jealous of his younger brother Pandu or his sons. Dhritarashtra could never accept this and he never did. Gandhari's children specially the eldest one, were as ambitious and jealous as their father. Gandhari did her mother's duty to the best of her ability to make her children accept their destiny and be happy with whatever their lot. The children never accepted this. Although sandwiched between a jealous and ambitious husband and an equally jealous and ambitious children, she was herself a God loving soul and respected