@inbook{NBERc1606,
 Crossref = "NBERunkn66-2",
 title = "Collection and Use of Job Vacancy Data in the Netherlands",
 author = "Lodewijk J. Niesten",
 BookTitle = "The Measurement and Interpretation of Job Vacancies",
 Publisher = "NBER",
 pages = "291-305",
 year = "1966",
 URL = "http://www.nber.org/chapters/c1606",
}
@book{NBERunkn66-2,
 title = "The Measurement and Interpretation of Job Vacancies",
 author = "NBER",
 institution = "National Bureau of Economic Research",
 type = "Book",
 publisher = "NBER",
 year = "1966",
 URL = "http://www.nber.org/books/unkn66-2",
}