CREATE VIEW list_people_presenation AS SELECT Person.firstname, Person.personRef FROM Person, Gives, PresentedBy, Presentation WHERE Person.personRef = Gives.personRef AND Person.personRef = PresentedBy.personRef AND Presentation.presNo = PresentedBy.presNo;

CREATE VIEW list_people_tutorial AS SELECT Person.firstname, Person.personRef FROM Person, Gives, Tutorial WHERE Person.personRef = Gives.personRef AND Tutorial.tutorialNo = Gives.tutorialNo;

SELECT DISTINCT * FROM list_people_presenation WHERE EXISTS(SELECT * FROM list_people_tutorial WHERE list_people_presenation.personRef = list_people_tutorial.personRef);