Jonzén, N.; Piacentini, D.; Andersson, A.; Montemaggiori, A.; Stervander, M.; Rubolini, D.; Waldenström, J.; Spina, F. The Timing of Spring Migration in Trans-Saharan Migrants: A Comparison Between Ottenby, Sweden and Capri, Italy. Ornis Svec 2006, 16, 27–33.