Former prime minister Manmohan Singh was admitted to AIIMS Delhi on Thursday evening after his health deteriorated, sources said.The 92-year-old Singh was brought to the emergency department of the hospital, they said. They said the condition of Singh was critical.The reason for his hospitalisation was not immediately known.Narendra Modi, Manmohan Singh Or Narasimha Rao: A Comparative Analysis Of Prime Ministers And Sensex Returns