Question: What was Nikola Tesla inventions that is what Guglielmo Marconi referred to?
Answer(s):
answer: Wireless telegraphy

SPARQL query:
PREFIX ns: <http://rdf.freebase.com/ns/>
SELECT DISTINCT ?x
WHERE {
FILTER (?x != ns:m.05d1y)
FILTER (!isLiteral(?x) OR lang(?x) = '' OR langMatches(lang(?x), 'en'))
ns:m.05d1y ns:law.inventor.inventions ?x .
?x ns:event.speech_topic.speeches_or_presentations_on_this_topic ?c .
?c ns:event.speech_or_presentation.speaker_s ns:m.035pm . 
}