What year was 'Automaten in planaren Graphen' published?
Mention the year in which 'Automaten in planaren Graphen' was published.
SELECT DISTINCT ?answer WHERE { <https://dblp.org/rec/journals/acta/Rollik80> <https://dblp.org/rdf/schema#yearOfPublication> ?answer }
<https://dblp.org/rec/journals/acta/Rollik80>