34 submanifold of $X$, then $X \setmin Y$ implicitly means the closure

    34 submanifold of $X$, then $X \setmin Y$ implicitly means the closure

    35 $\overline{X \setmin Y}$.

    35 $\overline{X \setmin Y}$.

    36 

    36 

    37 

    37 

    38 \subsection{Systems of fields}

    38 \subsection{Systems of fields}

    39 

    40 

    40 Let $\cM_k$ denote the category with objects 

    41 Let $\cM_k$ denote the category with objects 

    41 unoriented PL manifolds of dimension

    42 unoriented PL manifolds of dimension

    42 $k$ and morphisms homeomorphisms.

    43 $k$ and morphisms homeomorphisms.

    43 (We could equally well work with a different category of manifolds ---

    44 (We could equally well work with a different category of manifolds ---