What is {student of} of {Strabo} that is {sourcing circumstances} is {presumably} ?
Strabo's student was presumably known as who?
Who was presumably thought to be a student of Strabo?
SELECT ?a WHERE { resource:Strabo property:student_of ?z . ?z property:sourcing_circumstances resource:presumably . ?z property:student_of ?a }
select distinct ?obj  where {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q45936> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P1066> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> ?obj .
?statement <http://www.wikidata.org/entity/P1480> <http://wikidata.dbpedia.org/resource/Q18122778>
} 

SELECT ?obj WHERE { wd:Q45936 p:P1066 ?s . ?s ps:P1066 ?obj . ?s pq:P1480 wd:Q18122778 }