José Leonardo Ledea Rodríguez When the letters of the alphabet are insufficient to distinguish between means in a factorial arrangement, one option is to employ a different sort of label or notation. Instead of utilizing letters, you might use numbers or symbols to differentiate the methods. Another option is to combine letters with subscripts or superscripts, or a mix of letters and numerals.

Another option is to use software such as R and the'multcomp' package to do multi-comparison tests. Tukey, Holm, Bonferroni, and other p-value correction procedures are used in these programs.

Another option is to use the emmeans package and lsmeans. This package has a good summary, plot, and a variety of other helpful functions.

Finally, the idea is to utilize clear and consistent nomenclature that allows you to differentiate between the means in your research.

Fatemeh Khozaei Thanks very much for your attention to this question, same time for the observations and recommendations for the user's various statistical software.

Best regards.

Perhaps you can combine letters and numbers a01, a02, etc.

then indicate this in your table foot.

Dr Ofelia Andrea Valdés Rodríguez thanks very much.

Best regards