Interpolation by sums of the series of exponentials in $H (\mathbb C)$   with interpolation nodes on the rays
  In the space of all entire functions it is solved the problem of interpolation taking into account multiplicities by sums of the series of exponentials with the exponents from a given set. It is found a criterion of solubility of the problem in the case when all infinite portions of interpolation nodes are situated on a finite system of rays. It is also disclosed that the problem is equivalent to particular problems of simple interpolation, as well as of point-wise crude approximation, by sums of the series of exponentials. 
S.G. Merzlyakov, S.V. Popenov
math.CV