H. Mattison, J. Sehic, and H. Nybom, “Severely pollen-limited fruit set in a pear (Pyrus communis) orchard revealed by yield assessments and DNA-based paternity assignment of seedlings”, Int. j. hortic. sci., vol. 13, no. 3, pp. 67–74., Sep. 2007, doi: 10.31421/IJHS/13/3/749.