如何从Wikidata的SPARQL查询的输出中排除值？

如何解决如何从Wikidata的SPARQL查询的输出中排除值？

我正在尝试使用wikidata查询服务编写SPARQL查询，以检索1970年以来荷兰的所有总理。但是，我想通过检查总理是否曾在大学工作来过滤输出。如果部长在大学任职，则不应出现在结果中。

我认为我必须使用FILTER NOT EXISTS表达式，但不知道如何正确编写此行。有人可以帮我吗？

有关我的查询和输出，请参见以下内容：

SELECT ?pmLabel ?start ?companyLabel
WHERE
{   
  ?pm wdt:P39 wd:Q3058109.
  ?pm p:P39 ?posHeld.
  ?pm wdt:P108 ?company.
  ?posHeld ps:P39 wd:Q3058109.
  ?posHeld pq:P580 ?start.
    
  FILTER(year(?start) > 1970) 
  # FILTER NOT EXISTS(?company (something) "Universit") 
  SERVICE wikibase:label { bd:serviceParam wikibase:language "en". } # labels

 } 
ORDER BY DESC(?start)

+----------------------+------------------+------------------------------+
|  primeMinisterLabel  |      start       |         companyLabel         |
+----------------------+------------------+------------------------------+
| Mark Rutte           | 14 October 2010  | UniLever                     |
| Mark Rutte           | 14 October 2010  | Calvé                        |
| Jan Peter Balkenende | 22 July 2002     | Erasmus University Rotterdam |
| Jan Peter Balkenende | 22 July 2002     | Vrije Universiteit Amsterdam |
| Ruud Lubbers         | 4 November 1982  | United Nations               |
| Ruud Lubbers         | 4 November 1982  | Harvard University           |
| Ruud Lubbers         | 4 November 1982  | Tilburg University           |
| Ruud Lubbers         | 4 November 1982  | Hollandia                    |
| Dries van Agt        | 19 December 1977 | Kyoto University             |
| Dries van Agt        | 19 December 1977 | Radboud University Nijmegen  |
| Dries van Agt        | 19 December 1977 | Kwansei Gakuin University    |
| Dries van Agt        | 19 December 1977 | Ritsumeikan University       |
+----------------------+------------------+------------------------------+