@article{van Balen_2011, title={Short note on the occurrence of grey phase Black-headed Bulbul <em>Pycnonotus atriceps</em&gt; especially on Java}, volume={2}, url={https://kukila.org/index.php/KKL/article/view/24}, number={4}, journal={KUKILA}, author={van Balen, Bas}, year={2011}, month={Mar.}, pages={86-87} }