The phrase "acknowledged only once" is correct and usable in written English.
It can be used to indicate that something has been recognized or accepted a single time, without repetition.
Example: "The feedback from the client was acknowledged only once during the meeting, which led to some confusion later on."
Alternatives: "recognized just once" or "noted a single time".
The Pentagon has acknowledged only once before that American service members were inside Libya during the uprising — in March, when Marines rescued an American pilot who had ejected over the country while participating in a NATO airstrike.
The secret archive was held at Hanslope Park, north of London, and acknowledged only once historians employed by lawyers representing the Mau Mau veterans realised that some documents from the era were being withheld.
For the first time, the conservative establishment has admitted what it once acknowledged only in private: that Iran can no longer afford to snub the Great Satan.
She acknowledged only the hardship of finding decent bread in Boston, which she addressed by having her own delivered once a week by FedEx.
He was never shot down and acknowledged having been hit only once, when he was jumped by a group of Messerschmitts.
It will not be pleasant, Mr de Wit acknowledges, "but it's only once every 25 years".
It is only once we acknowledge the existence of these attitudes and identify the influences at work that we can deliver the right kind of educational interventions to help build capacity to resist racist ideas and attitudes among young people".
TO the best of my knowledge, Frank Sinatra acknowledged the existence of rap music only once in his life: at the lavish 1995 tribute in honor of his 80th birthday, after the hip-hop trio Salt-n-Pepa performed a special-lyrics version of their hit "Whatta Man," he turned to his wife, Barbara, and said, "Marvelous".
Only once did I acknowledge my roommate problems.
Only once does he acknowledge a significant error - when he appeared to endorse George Bush's tax cuts - and that was more of presentation than of substance.
Over the last decade or two, serious car collectors have increasingly acknowledged that a car can be original only once.
