Tom Henning Ovrebo, the referee of the controversial Champions League semi-final between Chelsea and Barcelona in 2009, has admitted that he made mistakes in the game that denied the Premier League side a place in the final.Ovrebo found himself at the centre of a firestorm at Stamford Bridge at the end of the second leg three years ago, having rejected four reasonable penalty claims from the home side - then managed by Guus Hiddink - during the 90 minutes, as they eventually went out to Andres Iniesta's last-minute strike.The Norwegian official was confronted by Michael Ballack and Didier Drogba even before the final whistle, and subsequently received death threats from a section of irate Chelsea fans. Ovrebo has now revealed that he still receives threatening messages, and has admitted that he did not enforce the laws correctly during the game at Stamford Bridge."I still get a few death threats, but they go straight into the garbage box. I don't take them seriously, although sometimes I wonder about the people who send them," Ovrebo told The Times. "Just yesterday I got an email from a Chelsea fan saying he wanted to kill me and my family."Everyone who knows the laws of the game knows I should have done things differently, but that's the life of a referee. In a strange way, I was actually satisfied with the way we all managed to keep calm in a tense situation."He added: "On the pitch I did my best. I shouldn't have to apologise as mistakes are part of the game."Drogba was subsequently given a five-game ban by UEFA for his outburst at the final whistle, with team-mate Jose Bosingwa given a three-game suspension. Ovrebo feels no ill-will towards the Ivorian, however, after the pair reconciled their differences at the disciplinary hearing."It was a very challenging match and with the angry scenes after the final whistle it became less enjoyable," Ovrebo noted. "Some players got too emotional and behaved badly, but no one got killed. It's important to put it into perspective."It helped me as a referee ... if I can cope with Drogba screaming at me, I can cope with anything - although he's a nice guy, really."The Blues have the chance to gain revenge on the Spanish club, as they face them in the Champions League semi-finals again this season. The first leg takes place at Stamford Bridge on Wednesday