private JTextField getJTextFieldPossibleLetters() {
		if (jTextFieldPossibleLetters == null) {
			jTextFieldPossibleLetters = new JTextField();
			jTextFieldPossibleLetters.setText("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz");
		}
		return jTextFieldPossibleLetters;
	}