A Correction to “Incidence Matrices and Collineations of Finite Projective Planes” by Chat Yin Ho, Designs, Codes and Cryptography, 18 (1999), 159–162

In this note we consider the set of incidence matrices of a cyclic projective planes whose set of points has cardinality a prime number p. We provide a correct proof of a result of Ho, showing that there exists an incidence matrix that possesses exactly p distinct eigenvalues.