Detailed representation of the [(C+N)/Fe] abundance ratio. Left panel: abundance ratio [(C+N)/Fe] vs. metallicity [Fe/H]. Stars with upper limits in C or N have not been considered. Right panel: [(C+N)/Fe] vs. [P/Fe]. Solid circles correspond to real measurements in P, and empty circles denote upper limits in P. In both panels, the error of [(C+N)/Fe] was defined as the quadratic sum of the standard deviation of the C and N measurements.