MONOS: Multiplicity Of Northern O-type Spectroscopic systems - I. Project description and spectral classifications and visual multiplicity of previously known objects
J. Maíz Apellániz, E. Trigueros Páez, I. Negueruela, R. H. Barbá, S. Simón-Díaz, J. Lorenzo, A. Sota, R. C. Gamen, C. Fariña, J. Salas, J. A. Caballero, N. I. Morrell, A. Pellerin, E. J. Alfaro, A. Herrero, J. I. Arias and A. Marco
