Svanes C, Dharmage S, Sunyer J, Zock JP, Norback D, Wjst M, Henrich J, Jarvis D, de Marco R, Plana E. Long-term reliability in reporting of childhood pets by adults interviewed twice, 9 years apart. Results from the European community respiratory health survey I and II. Indoor Air. 2008 Apr;18(2):84-92.