According to us, a double appearance of an identical indication (sempre forte) four bars apart may be a mistake of the engraver, who, apart from the correct place, unnecessarily repeated the indication a line higher or lower. Due to this reason, in the main text, we give the indication in bars 334-335 in a variant form (in brackets), being less justified after the 
in the previous bar.
In GE and EE, in both places, forte was replaced with a conventional 
mark.
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category imprint: Differences between sources; Editorial revisions
issues: EE revisions, GE revisions
notation: Verbal indications