['Within', 'such', 'a', 'framework', ',', 'comparisons', 'with', 'experiments', 'support', 'the', 'introduction', 'of', 'the', 'δ', 'meson', 'in', 'the', 'description', 'of', 'the', 'iso', '-', 'vector', 'equation', 'of', 'state', '.']