"Andrej Holm, from Berlin's Humboldt University, who specialises in urban gentrification, was arrested three weeks ago on suspicion of aiding a militant organisation suspected of carrying out more than 25 arson attacks in Berlin since 2001. In protest letters the academics from across Europe, the US and Canada said Mr Holm's arrest was based on his academic writings, and the evidence used to connect him to terrorism was at best flimsy."