set of all $\{y,f\}\in\tma$ such that $y$ has compact support. Then $\tma$ and $\cT_0$ are linear relations in $\lI$ and the Lagrange’s identity $$(f,z)_\D-(y,g)_\D=[y,z]_b -[y,z]_a,\quad \{y,f\}, \; \{z,g\} \in\tma.$$ holds with $$\label{1.11}
[y,z]_a:=\lim_{t \downarrow a}(J y(t),z(t)),\qquad [y,z]_b:=\lim_{t \uparrow
b}(J y(t),z(t)), \quad y,z \in\dom\tma.$$ By using introduce also the linear relation $\tmi$ in $\lI$ by $$\label{1.12}
\tmi=\{\{y,f\}\in\tma:\,[y,z]_a= [y,z]_b=0, \; z\in\dom\tma\}.$$ Moreover, in the case of the regular endpoint $a$ (that is, if $a\neq -\infty$ and $B(t)$ and $\D(t)$ are integrable on $(a,\b), \;\b\in\cI$) let $$\label{1.13}
\cT_a=\{\{y,f\}\in\tma:\, y(a)=0 \;\;\text{and}\;\; [y,z]_b=0, \;
z\in\dom\tma\}.$$ All the above relations in $\lI$ naturally generate by means of the equalities $$\begin{gathered}
\Tmi=\{\{\pi y, \pi f\}:\{y,f\}\in\tmi\}, \;\; \;\;\;T_a=\{\{\pi y, \pi
f\}:\{y,f\}\in\cT_a\},\label{1.14} \\
 T_0=\{\{\pi y, \pi f\}:\{y,f\}\in\cT_0\},
\;\;\;\;\;\Tma=\{\{\pi y, \pi f\}:\{y,f\}\in\tma\} \nonumber\end{gathered}$$ linear relations $\Tmi, \; T_a, \; T_0$ and $\Tma$ in the Hilbert space $\LI$.

As was shown in [@Orc] (see also [@LesMal03; @BHSW10]) in the case of the *definite system* $T_0$ is a symmetric linear relation in $\LI$, $\Tmi$ is closure of $T_0$ and $\Tma=\Tmi^*(=T_0^*)$; moreover, if the endpoint $a$ is regular then $\Tmi=T_a$. In view of this assertion $\Tmi$ and $\Tma$ are called minimal and maximal relations respectively, which is in full accord with similar definition 