Adri di Groot's book is based on Plichta's original ideas. What concerns prime number reciprocals, Groot goes even beyond Plichta and this makes his book a contribution which should not be overlooked. But Groot understands only partly the pivotal role of the golden mean and the relationship between the prime number cross, Pascal's triangle and the golden mean.
In this context, the reader should be aware that Jan Boeyens, one of the leading professors of theoretical chemistry, is confronting the main stream theories of relativity, quantum theory, wave-particle duality, orbital angular momentum, atomic shape and chemical bonding in the second part of his book Chemistry from First Principles with an alternative theory of the periodic laws, chemical interaction, structure theory and even cosmology. This truly extraordinary book has to be seen as an extension of his monograph on The Periodicity of Atomic Matter, and both books are rooted in Plichta's original ideas of the prime number cross.