Integration test post
At first, we sample 
in the 
( is odd) equidistant points around 
:
[
f_k = f(x_k),: x_k = x^*+kh,: k=-frac{N-1}{2},dots,frac{N-1}{2}
]
where 
is some step.
Then we interpolate points 
by polynomial
begin{equation} label{eq:poly}
P_{N-1}(x)=sum_{j=0}^{N-1}{a_jx^j}
end{equation}
Its coefficients 
are found as a solution of system of linear equations:
begin{equation} label{eq:sys}
left{ P_{N-1}(x_k) = f_kright},quad k=-frac{N-1}{2},dots,frac{N-1}{2}
end{equation}
Here are references to existing equations: (ref{eq:poly}), (ref{eq:sys}).
Here is reference to non-existing equation (ref{eq:unknown}).
