BTW, this is not a real referendum, as there are no guarantees. Of course, the reason why there are no democratic guarantees is because of the actions of the Spanish government. But you can see the "high degree" census control here in this video: https://elpais.com/Comentario/1506857481-5be7eb5d11476b5cac1...
But I also have to say that there is certain hypocrisy in all this. Pro-independence people already have the pictures and excuses they wanted: Catalans voting and the Spanish police exercising violence. But, if Catalonia became independent, they would also have a police, a repressive force. So you can see how the excuse for creating a new State, violence of the State, is hypocritical for an economic liberal like me.