For some information and further references concerning the functional equations in single variable we refer to [15 17]; for an ample survey on stability results for those equations see [2].
Since then numerous papers have been published on that subject and we refer to [2 7] for more details, some discussions and further references; for examples of very recent results see, for example, [8 12].
For further discussion, some excerpts and further references, see Pines 1963, lix ff.
Various equations of Kirchhoff type have been studied by many authors, especially after the work of Lions [2], where a functional analysis framework for the problem was proposed; see e.g. [3 6] for some interesting results and further references.
This last provides a very useful brief account also of some other fourteenth century views, with further references.
For more information and further references concerning the subject, we refer the reader to [27 29].
Because this is not nearly enough in the double-entendre department, the horns also yield some further musical references.
We refer the reader to [10 14] for further references.
We refer to [12] for an excellent overview and further references.
We refer the reader to the publications in the bibliography for further references.
