A short service was held yesterday in memory of a young census collector murdered by the IRA.
Joanne Mathers (29) was gunned down as she collected census forms in the Gobnascale area of Londonderry in 1981.
Her killer has never been caught and the £20,000 reward posted in 2012 by her husband Lowry remains unclaimed.
One of Mrs Mathers' friends, Mary Casey, paid tribute to her yesterday, recalling a "quiet, smiling, wonderful lady".
Mrs Casey said: "I really can't believe it has been 40 years since Joanne was so cruelly taken from us.
"Joanne and I played squash in the City of Derry Ladies Squash club and we played in venues all over Northern Ireland.
"Our club was cross-community and we had no interest in what anyone's religion or politics were - we were a group of young women who enjoyed each other's company and playing squash.
"We laughed together, talked about the things young married women talk about and looked out for each other wherever we went playing squash.
"I will always remember Joanne as a quiet, smiling, wonderful lady and whenever I meet with any of the other ladies who were in our club we often talk about what happened to Joanne and remember her with deep affection."
Mrs Mathers' husband and son remembered their loss privately, but they were prayed for during a short service of remembrance conducted by Rev Alan Irwin, organised by South East Fermanagh Foundation.
Rev Irwin said: "The census has been very much to the fore in recent days, but sadly 40 years ago the completion of the census was given that same importance by republicans, who boycotted it in 1981 with claims about gathering intelligence.
"Undeniably there was no justification of what led from that boycott - the murder of census worker Joanne Mathers.
"It was an indefensible, ruthless and callous act and their actions left behind a grieving husband and family to pick up the pieces.
"We remember Joanne's family as we acknowledge another significant anniversary and it is to Joanne that we pay tribute and seek to remind the next generation of the truth of terrorism, the real cost of terrorism."