protected abstract string ConvertTo(BoldTxt boldText);
protected override string ConvertTo(BoldTxt boldText) { return "<b>" + boldText.Content + "</b>"; }
protected override string ConvertTo(BoldTxt boldText) { return("**" + boldText.Content + "**"); }
protected override string ConvertTo(BoldTxt boldText) { return("\\textbf{" + boldText.Content + "}"); }