input: 2; output: 2; aliases: LETTER = ([GREEK CAPITAL LETTER ALPHA WITH TONOS]-[GREEK LETTER YOT] | [GREEK SMALL LETTER ALPHA WITH VARIA]-[GREEK CAPITAL LETTER OMEGA WITH PROSGEGRAMMENI]) ; expressions: {LETTER}`'' => \1 [GREEK PSILI] ; `''{LETTER} => [GREEK PSILI] \1 ; {LETTER}[RIGHT SINGLE QUOTATION MARK] => \1 [GREEK PSILI] ; [RIGHT SINGLE QUOTATION MARK]{LETTER} => [GREEK PSILI] \1 ; . => \1;