As vigils to mark the 37th anniversary were held around the world, Chinese authorities reportedly banned families of those who died in 1989 from visiting their graves.

Amid growing censorship at home under the rule of Xi Jinping, efforts to document the massacre of 4 June, 1989, are intensifying abroad

Vigils marking anniversary have shifted to overseas cities in past years

Thirty-seven years ago, China's military violently ended pro-democracy protests in Beijing's Tiananmen Square. The government has never released a full death toll, with estimates…