The reaction of 1-Bromo-3-Chlorocyclobutane with 2 equivalents of Na in the presence of ether products:
The reagent of Na/(in dry ether) is indicative of Wurtz reaction.
Now 2 equivalents of na is explicity (clearly) mentioned.
Above is an example of intramolecular Wurtz reaction
Also,
Intramolecular Wurtz reaction.