[1] Together with his colleague Hans Horsten, he conducted research into the Dutch Civil Servants Pension Fund, which turned out to receive extra subsidies due to fraud.
State secretary Gerrit Brokx had to resign in 1986 as a result of the affair and a parliamentary inquiry into construction subsidies followed later that year, led by Klaas de Vries.
[2] Heijboer was convinced that the Parliamentary Commission of Inquiry had not found the truth about the disaster; according to him, El Al's Boeing 747 had been a military aircraft.
Under the name Het Klankbord (The Sounding Board) he collected facts about the Bijlmer disaster that were concealed during the parliamentary inquiry.
[6] At the end of his life, Heijboer researched the experiences of Dutch and Indonesian soldiers during the skirmishes in West New Guinea in 1962.
[7] He attended the Hogere Burgerschool and the Kweekschool voor onderwijzers (Training school for teachers) and then took a journalism course in Nijmegen.