### Matrix for z(3,3 | 3,3)

$I$ | $I$ | $\alpha$ |

$I$ | $\alpha$ | $I$ |

$\alpha$ | $I$ | $I$ |

$I$ is the identity and $\alpha$ is a 3-cycle. The $I$ entries form an extremal 3x3 rectangle-free matrix, showing that the finite projective plane of order 3 is sub-similar.

$I$ | $I$ | $\alpha$ |

$I$ | $\alpha$ | $I$ |

$\alpha$ | $I$ | $I$ |

$I$ is the identity and $\alpha$ is a 3-cycle. The $I$ entries form an extremal 3x3 rectangle-free matrix, showing that the finite projective plane of order 3 is sub-similar.