CNO behaviour in planet-harbouring stars - I. Nitrogen abundances in stars with planets L. Suárez-Andrés, G. Israelian, J. I. González Hernández, V. Zh. Adibekyan, E. Delgado Mena, N. C. Santos and S. G. Sousa A&A, 591 (2016) A69 Published online: 16 June 2016 DOI: 10.1051/0004-6361/201628455