The letters released on Thursday were sent to powerful US senators John McCain and Carl Levin.
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Browne would not comment on what specific threats were made or where the letters were postmarked.
The museum bought the letters from an anonymous private collector via Sotheby's in New York.
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How did he react to the briefings about the letters that were addressed to him?
The letters complained "no one wanted to listen to me before, " according to the affidavit.
Several of the letters attributed to Paul were in all likelihood not written by Paul.
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Curtis also had posted language similar to the letters on his Facebook page, the affidavit says.
But the letters to Margrethe showed that his transition to Cambridge intellectual circles was turbulent.
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The FBI said there was no indication of a connection between the letters and the bombing.
White House spokesman Jay Carney said the president had been briefed on the letters.
The letters were signed, "I am KC and I approve this message, " the source said.
If the letters section in local newspapers is any indication, those in power need not worry.
Her Majesty's post office already has a 30-year franchise to deliver the letters in Argentina.
Deutsche Post has been partially privatised but retains a lucrative monopoly of the letters market.
The letters, she later learned, stood for bilateral tubal ligation, a form of sterilization.
On Friday he told the BBC that Porsche "has agreed to partially release" the letters.
The letters were among a collection loaned by Nussey to Bronte's biographer Elizabeth Gaskell in 1857.
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The letters will use a mix of messages, including some offering recipients a savings-account feature.
Dr. Mikovits, who confirmed the letters, said she hadn't received a response in return.
One of the letters discovered by archivists was from Lord Melville, First Lord of the Admiralty.
Mounted copies of the letters will now be presented to the Lieutenant Governor of Manitoba.
The letters were still inside the en-velopes, so I took them out and read them.
After skimming a few histories, I dug deeper, reading the letters and journals of early explorers.
Now the letters have been retranslated, comprehensively annotated and there are 20 new items.
When the letters resume, Vincent refers to himself as a prisoner, a caged bird.
In one of the letters she asks Sir Thomas to come and see her.
The letters "FONTAINE" might be visible on the back of a jersey in a random highlight.
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Greenspun and Jonathan Shapiro said prosecutors were required to turn over the letters, but did not.
The letters about the death in 1876 are on display at the Cheshire mill.
But in 1982 a Swiss scholar thought the tablets and the letters came from Celtic times.
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