[UPDATE (1/16): The Mostar diocesan website has picked up this translation of Bishop Peric's statement, and improved it in a few places, so I recommend readers use that edition. I'll leave this draft here, along with my introductory comments.]
One sensational element of the claimed apparition at Medjugorje is in predictions of a "great sign" to eventually appear at the town. According to the alleged seers, the sign would be a miraculous proof of the alleged apparitions' validity, and as such would encourage the world to repent. The "sign" was part of ten apocalyptic "secrets" that the apparition supposedly told to the seers.
On December 11, Bishop Ratko Peric of the diocese of Mostar-Duvno issued a paper relating how this idea got started, and what the seers have said and done in regard to it. This document highlights various contradictions among the seers vis-a-vis each other, and inconsistencies between their earlier and later statements.
It also looks at the apparent falsehoods claimed by "seer" Ivan Dragicevic, who at one point wrote down a prediction of the sign, and later denied having written it.
Bp. Peric begins by addressing the contention of some apparition promoters that all the talk of a "great sign" was invented by other people, and does not come from the seers themselves. Then he proceeds in chronological order through various diaries, books, chronicles, and interviews to present how the idea of the "great sign" first appeared. He also recounts the efforts of two study commissions to explore the question, efforts that were somewhat thwarted by the non-cooperation of the seers.
This document was published on the diocesan website in Croatian and in Italian, and here I present an English translation based on the Italian.
By way of full disclosure: please be aware that I am an amateur in learning the Italian language; any errors or omissions are my responsibility, and I appreciate any appropriate corrections. [Thanks to Marco Corvaglia for sending a correction already.]
[One technical note: the translation of the key words apparizione and apparsa needs a little explanation. Apparizione refers to an apparition as an event; apparsa to the personage or entity that appears. Apparsa, in the feminine gender, indicates a feminine being. In English, both of these words might be translated as "apparition". However, to do so would lead to obscurity, especially in sentences containing both words. Therefore, I translate apparizione as "apparition" and apparsa as "lady". This does not imply any endorsement of the alleged seers' reports.]
To begin with a sample, here is a quotation from Bp. Peric's conclusions:
"The sign" has to be, and may indeed be, the most splendid weapon of the "seers" of Medjugorje and of the propagandists of the "apparitions". The same "seers", from the beginning, have asked the lady that appeared to them for it. They asked for it and "begged" for it, as we have seen. Then, through the "seers", followed whole floods of lies, contradictions, promises, speed-ups, slowdowns, falsehoods, uncertainties.