### A survey on nonlocal boundary value problems.

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This is a survey of known results on estimating the principal Lyapunov exponent of a timedependent linear differential equation possessing some monotonicity properties. Equations considered are mainly strongly cooperative systems of ordinary differential equations and parabolic partial differential equations of second order. The estimates are given either in terms of the principal (dominant) eigenvalue of some derived time-independent equation or in terms of the parameters of the equation itself....

The aim of this paper is to give an existence theorem for a semilinear equation of evolution in the case when the generator of semigroup of operators depends on time parameter. The paper is a generalization of [2]. Basing on the notion of a measure of noncompactness in Banach space, we prove the existence of mild solutions of the equation considered. Additionally, the applicability of the results obtained to control theory is also shown. The main theorem of the paper allows to characterize the set...

Existence of nonnegative solutions are established for the periodic problem ${y}^{\text{'}}=f(t,y)$ a.eȯn $[0,T]$, $y\left(0\right)=y\left(T\right)$. Here the nonlinearity $f$ satisfies a Landesman Lazer type condition.

In this expository paper we consider various approaches to multisummability. We apply it to nonlinear ODE's and give a somewhat modified proof of multisummability of formal solutions of ODE's with levels 1 and 2 via Écalle's method involving convolution equations.

The paper describes the general form of functional-differential equations of the first order with $m(m\ge 1)$ delays which allows nontrivial global transformations consisting of a change of the independent variable and of a nonvanishing factor. A functional equation $$f(t,uv,{u}_{1}{v}_{1},...,{u}_{m}{v}_{m})=f(x,v,{v}_{1},...,{v}_{m})g(t,x,u,{u}_{1},...,{u}_{m})u+h(t,x,u,{u}_{1},...,{u}_{m})v$$ for $u\ne 0$ is solved on $\mathbb{R}$ and a method of proof by J. Aczél is applied.

The paper describes the general form of an ordinary differential equation of the second order which allows a nontrivial global transformation consisting of the change of the independent variable and of a nonvanishing factor. A result given by J. Aczél is generalized. A functional equation of the form $$f(t,vy,wy+uvz)=f(x,y,z){u}^{2}v+g(t,x,u,v,w)vz+h(t,x,u,v,w)y+2uwz$$ is solved on $\mathbb{R}$ for $y\ne 0$, $v\ne 0.$