Find the years in which the authors of 'The Digital Approximation of Contours' published other papers.
The authors of 'The Digital Approximation of Contours' published in which other years?
SELECT DISTINCT ?answer WHERE { <https://dblp.org/rec/journals/jacm/Mason56> <https://dblp.org/rdf/schema#authoredBy> ?x . <https://dblp.org/rec/journals/jacm/Mason56> <https://dblp.org/rdf/schema#yearOfPublication> ?y . ?z <https://dblp.org/rdf/schema#authoredBy> ?x . ?z <https://dblp.org/rdf/schema#yearOfPublication> ?answer FILTER (?answer != ?y) }
<https://dblp.org/rec/journals/jacm/Mason56>