The phrase "a sole instance" is correct and usable in written English.
It can be used to refer to a single occurrence or example of something.
Example: "In this study, we found a sole instance of the phenomenon occurring under specific conditions."
Alternatives: "a single instance" or "one occurrence".
The conundrum of umpiring is neatly posed by the peculiar rule of the knee-to-shoulder strike zone, which Mr. Weber calls the sole instance of a playing area that is demarcated only in the minds of officials.
It is the sole instance in which a member of the Israeli forces was charged for killing a Palestinian child.
The effect on audiences of watching Gethin follow McBrain helps explain why a behavourial psychologist friend of Griffiths once remarked that Comedians was the sole instance in his theatregoing experience "where you're invited to laugh, and then get punished for it".
The sole instance of female dominance is one Philippine study with a ratio of 32% males from a small sample size of 32 individuals [31].
This is the sole instance where deep perspective is used, making the faces and bodies appear more solid, and perhaps, closer to the here and now.
It was the sole instance in which slavery reparations were authorized — and it compensated slaveholders in Washington, D.C., for the cost of emancipating their human chattel.
Torture of Women (1976), is the best known of these; the Serpentine's selection has bypassed this, and Marduk (1986) looks to be the sole instance on show.
The teams each took four shots on goal in the first period, but the Devils' sole instance of disorganized defense led to Hagelin's goal.
So there is at least one property that is self-instantiating: it has itself as its sole instance, and indeed as its sole possible instance.
The results showed that damage increased with the level of the highest impact event in each sequence; For instance, a sole impact of 3 J was more detrimental in terms of cumulative damage than multi-impact events.
