Minimal superpermutation length $L(3)$

IntegralPython, via Wikimedia Commons. CC BY-SA 4.0.
The shortest length of a string that contains each permutation of $3$ symbols as a substring.
Value: $9$
Updates
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Lower bound: $9$
Reference unknown
[via Superpermutations - Greg Egan] -
Upper bound: $9$
Reference unknown
[via Superpermutations - Greg Egan]