To : Lurking
there seems to be various opinions among priests. Could you cite an authoritative source especially one which is published an accessible? Your help much appreciated.
The authoritative source was my Humanae Vitae quote above.
Persona Humana (see
here) is also worth reading. For example:
This same principle, which the Church holds from Divine Revelation and from her authentic interpretation of the natural law, is also the basis of her traditional doctrine, which states that the use of the sexual function has its true meaning and moral rectitude only in true marriage.
…
This opinion is contrary to Christian doctrine, which states that every genital act must be within the framework of marriage.
…
The main reason is that, whatever the motive for acting this way, the deliberate use of the sexual faculty outside normal conjugal relations essentially contradicts the finality of the faculty.
All deliberate exercise of sexuality must be reserved to this regular relationship.
Putting it all together: Genital stimulation is only moral within the context of the marital act, which to be moral must take place within completed, non-contracepted intercourse.