Prime Minister Narendra Modi on Monday paid tributes to former prime minister Atal Bihari Vajpayee on his 99th birth anniversary, saying he worked to speed up the country's development all his life. PM Modi, along with President Droupadi Murmu, her predecessor Ram Nath Kovind, Lok Sabha Speaker Om Birla and several ministers paid tributes to the BJP stalwart at his memorial 'Sadaiv Atal' here.