Hi, augusta. I'm new here. Pleased to meet you.
The Greek letters seem to be simply text that's been selectively switched from an English to a Greek typeface by the publishers to avoid revealing what the letter actually contains, to continue piquing our curiosity so we'll buy the book :-) The text is presented in such a way as to make it difficult, if not impossible, to select and copy the text, then paste it into a page layout where all the text could be set in an English typeface.
It would be possible, though tedious, to reproduce the letter with English and Greek letters (assuming you have a Greek font on your computer), then run the result through that process. Me? Nah. I'm goin' to lunch
