The Polish website of the SSPX, is carrying a translation of the French District Superior's letter of May 17, 2012. The French translation may be read here.
The Polish text or introduction is as followed (translated by Barona):
To this appeal, the text [Fr. ] of which we present below; support was also given by the district superior of eastern Europe, Fr. Karol Stehlin, FSSPX.
The original Polish link may be read here.