(i) the slope for short-lived nuclides in the average interstellar medium in such a diagram is always 1.

(ii) for molecular clouds, the slope is expected to be 2 or slightly less than 2 for a model where the molecular clouds are at a steady state and slowly exchange matter with the remaining interstellar medium. The existing data suggest a residence time of ~6 x10⁷ yrs for the matter present in molecular clouds.

(iii) the intercept depends on (1) the residence time of matter in molecular clouds, (2) the mass fraction of the interstellar medium that is in molecular clouds, (3) the age of the galaxy and (4) the ratio of the time-average nucleosynthtic production rate and the production rate at the time of solar system formation.

(iv) the abundances of ⁵³Mn, ¹⁸²Hf, ²⁴⁴Pu and ¹⁴⁶Sm in the early solar system are likely formed by the same type of supernova sources (SNII?) over the history of our galaxy, while ¹²⁹I (and possibly ¹⁰⁷Pd) were produced in a different type of supernova sources (SNIa?) with the production rate skewed toward the early history of our galaxy. The abundances of these nuclides most likely characterize the average ISM values modified during their residence in the molecular cloud complex where the solar system formed. The abundances of ²⁶Al, ⁴¹Ca and ⁶⁰Fe are too high to be of galactic production; these must be a contamination from young stellar sources that formed within the proto-Solar molecular cloud. These young sources could not have contributed significant quantities of ⁵³Mn, ¹⁸²Hf, ²⁴⁴Pu and ¹⁴⁶Sm or ¹²⁹I and thus were dissimilar to typical supernova sources.