Under the general agreement about an exchange of researchers between Swedish Universities and SO AN in Novosibirsk, the authors invite A.Ershov to visit Sweden during the early fall of 1971.

The author thanks for the research reports and suggests to discuss a date of addressee's visit. Something like October 1 would be suitable for them.

The author suggests to the addressee to spend the first week after the IFIP conference in Lund and the next week in Stockholm.

During the stay at Lund University A.Ershov meets with colleagues Dahlstrand, Sigbo, Ekenberg, Nilsson and Pettersson and clears up their activities.