Ok when trying to think! a little about it, off course these ranges of the stopped notes are not possible, especially taking into account that the violinist has to touch a fourth higher than the stopped pitch.
As I said you can notate all harmonics sounding with the ° symbol. But if you want a specific artificial harmonic on a specific string notate the fixed finger with a normal and the touching finger with a diamond notehead.
It looks incomplete, misleading and wrong (just like most AI generated solutions)
It is simply physics.
There are certain notes (positions) on a string that will (when lightly touched) excite a particular harmonic of that string.
eg. half the length of the string will produce the octave.
It only appears complicated because the same harmonic note can be produced from 2 different places (one near the bridge and the other near the scroll)
These are all natural harmonics (artificial harmonics, which are also explained in the book are actually easier!!)
(Possible?) Ranges for artificial harmonics:
Violin: Stopped notes (G3–D6) → harmonics (G5–D8)
Viola: Stopped notes (C3–G5) → harmonics (C5–G7)
Cello: Stopped notes (C2–D5) → harmonics (C4–D7)
Of course some of these are possible to play using natural harmonics as well. For this, I’ll look at the chart for naturals if I’d like that particular sound.
How does these revised ranges look?
Thanks for the patience Janus 
It makes sense that it’s simply physics, Pythagoras and all 
But for me it’s even more complicated because I don’t know the ranges - when do the harmonics start and stop for the respective instruments? I can easily look up the normal range of the instruments, but the ranges for the harmonics is just as necessary.
What I’d prefer is when working on a piece, I enter a note for one of the three instruments in Dorico and check: “Can this actually be done?”- and then having the option of just looking a some text document telling me a short yes ( natural or artificial) or no (pick another note) 
Wrong! C2 is the bottom note of the cello (C4 is middle C in common parlance), so cannot be ‘stopped’.
Natural harmonics can only produce the notes from the harmonic series for that string (where the open string is the fundamental).
Artificial harmonics are a completely different kettle of fish.
Ok, sorry if I’m unclear 
These “revised ranges” are for artificial harmonics
Except, once again they are incomplete.
Yes, you can get the double octaves with artificial harmonics at the fourth (though the bottom one is a natural harmonic on the open string), but a different set with harmonics at the fifth (sometimes problematic because the the stretch required) and the major third are also possible (some will resonate more easily than others)
Thanks Janus and sorry if I upset you :-/
Really good to know that the ranges are correct (but incomplete and that some of them are actually natural harmonics). For me - if these ranges are possible, that’s already giving me a lot of options.
Maybe after some time I’ll look into which of the fifth and major third harmonics are actually possible and add them to the available options.
I’m not at all upset.
For non-string players, how harmonics work can be very confusing. (and the dorico implementation is still incomplete for playback)
I’m glad you are not
If you ignore the XIX century method I posted (the yellowish paper picture), the other attachments I posted above should be quite clear and, most of all, quite correct and comprehensive.
Is there something specific in them which you find confusing or unclear?
@MicheleGalvagno well first of all sorry for not really getting back to you after all you added to the post!
I think the Strings Natural Harmonics Chart and the String Harmonics Formulas you did are quite clear!
However for my use as a beginning composer - with very limited knowledge of these fantastic instruments I’m only scratching the surface.
That’s why my initial question maybe was indicating that I knew more than I actually do and also didn’t indicate clearly that my aims are understanding the score I’m currently analyzing, my future possibilities composing with harmonics and postponing more deep knowledge about how to actually produce them to the future.
That’s why I actually hijacked my own thread after your contributions, shifting my focus to getting to know which notes (instrument, note and octave number, and using which technique - natural or artificial) - that can be played “easily” by “any” semiprofessional or professional player. Without actually knowing how to produce them, which string to use, how to execute them etc. It’s simply too hard for me to grasp here in this first round.
It seems that with the help of all your contributions, I now have a list with 1st and 2nd natural harmonics and ranges of artificial harmonics using touch 4th only -which I’m really happy to start using in my composing endeavors 
one detail that is worth remembering:
the longer and thicker the string, the more easily natural harmonics can be produced.
as a rule of thumb, personally, I avoid anything other than touch 4th harmonics on the violin. I’ve simply had too many experiences where the violinists (all quite competent musicians) were simply not able to get touch 3 or touch 5 harmonics to sound at all (they really had to dig around on the string before getting the correct sound.)
on viola, touch 5 is a bit more accessible than for the violin, it does tend to speak better. The violist for whom I wrote my viola concerto had no problems after a first few tentative readings.
cello has access to more natural harmonics, simply because its strings are longer (thus the finger has a tiny bit more leeway to hit that sweet spot for the harmonic), so they (as soloists, but I’d avoid writing too many esoteric harmonics for a section) have access to touch minor 3rd, major 3rd, 4th, 5th, 6th, and a few more. I’ll let string players get into more detail about which extended harmonics are possible.
And of course, the contrabass, with its VERY long and thick strings, has considerably more variety of natural harmonics.
This, however, has a drawback: in lower positions some artificial harmonics require quite large hands.
Take what you will from my experience, I prefer to play a bit on the safer side. It lets me take into account technical difficulty when writing for a specific performer or ensemble.
But the best advice is: grab a cellist off the street and ask, beg, cajole, bribe, them into showing you precisely which natural and artificial harmonics they can play securely.
Remember that if it’s too esoteric this will cause insecurity in the performance. You want the musician to be able to play it musically without having to worry about whether or not their finger is landing on the exact right spot for a specific harmonic.
@Michel_Edward thanks so much for your input! Good point “the longer and thicker the string, the more easily natural harmonics can be produced.”
And also the potential artificial harmonics pitfall for the bigger of the instruments - that they need to be able to stretch their fingers more.
I’m definitely gonna play it safe, that’s why I only want to use the 1st and 2nd natural and touch-fourth artificial harmonics.
So, according to what I know until now, the natural list of notes are:
And the artificial ranges (off course some of these are open strings/naturals):
Violin: Stopped notes (G3–D6) → harmonics (G5–D8)
Viola: Stopped notes (C3–G5) → harmonics (C5–G7)
Cello: Stopped notes (C2–D5) → harmonics (C4–D7)
I slightly disagree. Certainly the longer the string the easier it is to find the harmonic. But thicker strings are generally harder to make ‘speak’ and that applies to both stopped notes and harmonics. (I find it much easier to sound harmonics on my violin than my viola)
That’s not even getting into the weeds, like doing artificial harmonics from natural harmonics, i.e., you can lightly touch a natural harmonic node and then also lightly finger a touch fourth above, and it’ll give a note 2 octaves above the natural harmonic.
note taken.
I’m just going by what the doublebass players I’ve spoken to have told me.
Personally, I find playing harmonics much easier on my viola than violin.