  The hypothesis that there exists a nonet of scalars mainly composed of a
valence quark-antiquark pair and mixed according to near singlet-octet
separation : f_0 (980) singlet, a_0^{+,0,-} (980), K^{* +,0}_0 (1430), \bar
K^{* -,0}_0 (1430), f_0 (1500) octet, is put to further tests from the three
body decays D^{\pm}, D_{s}^{\pm} -> PS^{\pm} pi^+ pi^- with PS^{\pm} =
pi^{\pm}, K^{\pm}. The analysis of decay phases supports the singlet nature of
f_0 (980).
