${\displaystyle \mathbb {N} {\mbox{ of natural numbers}}}$

${\displaystyle \mathbb {D} {\mbox{ is the open disc domain}}}$

${\displaystyle \mathbb {b} {\mbox{ is the open domain nature boundary}}}$

${\displaystyle \mathbb {C} ^{\pm }{\mbox{ is the complex half-plane}}}$

${\displaystyle mega{\mbox{ is a root of unity}}}$

${\displaystyle \nabla {\mbox{ is the gradient}}}$

${\displaystyle \Delta =\nabla \cdot \nabla {\mbox{ is the Laplace operator}}}$

${\displaystyle \Lambda {\mbox{ is Dirichlet-to-Neumann operator}}}$

${\displaystyle D_{x}{\mbox{ is a diagonal matrix w/the vector }}x{\mbox{ on the diagonal }}(D_{x}1=x)}$

${\displaystyle D_{A}{\mbox{ is the diagonal matrix, coinciding on diagonal w/the matrix }}A}$

${\displaystyle y,\lambda {\mbox{ is eigenvalue of operator/matrix}}}$

${\displaystyle ma(A){\mbox{ is spectrum of matrix }}A,{\mbox{ zeros of characteristic polynomial }}}$

\rho(A) \mbox{ is the characteristic polynomial of matrix } A

\tau \mbox{ is the Cayley transform}

${\displaystyle ega{\mbox{ is a continuous domain}}}$

${\displaystyle G/G^{*}{\mbox{ is graph or network and its dual}}}$

${\displaystyle V_{G}{\mbox{ is the set of vertices of a graph}}}$

${\displaystyle E_{G}{\mbox{ is the set of edges of a graph}}}$

${\displaystyle M_{G}{\mbox{ is the medial graph of an embedded graph }}G}$

${\displaystyle c{\mbox{ is conductivity}}}$