What was the topic of Ferdinand de Saussure's doctoral thesis, and what degree did he acheive at Leipzig University?
SELECT ?value1 ?value2 WHERE { wd:Q13230 p:P69 ?s . ?s ps:P69 wd:Q154804 . ?s pq:P1026 ?value1 . ?s pq:P512 ?value2 }
ferdinand de saussure: Q13230 leipzig university: Q154804