Double Implication Chain
A Double Implication Chain or DIC is a Forcing Chain with implications in both directions. When it starts and ends with the same cell, it is also a Nice Loop. When the nodes in the chain are candidates, it is also known as an Alternating Inference Chain.
Follow the links to these articles for more details about the use of chains:
The name is sometimes mistakingly interpreted as a "pair of implication chains", which are used in detecting a verity.