The BJP has sent legal notice to historian Ramachandra Guha, who had alleged that journalist Gauri Lankesh's killers could be from the Sangh Parivar - a group of organisations led by the Rashtriya Swayamsevak Sangh (RSS), the BJP's ideological mentor. Mr Guha has been warned of civil and criminal action if he doesn't offer an unconditional apology within three days for his comments, the BJP has said.