The terms of reference for an analytical report on collusion in relation to murders known as the Glenanne Series has been agreed.
The Glenanne Series relates to a significant number of murders and other offences committed in both Northern Ireland and the Republic of Ireland in the 1970s.
The Glennane group was suspected of involvement in up to 90 attacks.
These include the 1974 Dublin and Monaghan bombings where 34 people died, and the killing of members of the Miami Showband in 1975.
There have been consistent allegations that the loyalists had direct links to elements of the security forces in Northern Ireland.

The Terms of Reference (ToR) for the review were announced following agreement from PSNI Chief Constable Simon Byrne with Kenova lead investigator, and retired chief constable, Jon Boutcher.
Last November, Mr Boutcher agreed to carry out what is described as an analytical report on collusion into incidents involving the loyalists who were linked with more than 100 murders, mainly in the Tyrone and Armagh areas, in the 1970s and 1980s.
An independent team, led by Mr Boutcher, will be tasked with identifying the composition of the Glenanne Series and to establish whether the review of the cases as a whole suggests there were wider issues of collusion.
It will also include examining issues beyond those that have already been established.
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"I have already met a number of families affected by these incredibly sad events and have been touched by their great strength and the honesty and integrity of their efforts to find the truth," Mr Boutcher said.
Speaking of how moved he was by the families' stories, Mr Boucher said he was determined to "to apply the same rigour and focus to this review as has been undertaken throughout the other Kenova matters under investigation".
"Our aim is to find the truth for the families and be in a position to answer their previously unanswered questions," Mr Boutcher said.