De Beer Jaa.
Maandstat Bevolking. 1985 Jun;33(6):44-50.
PMID: 12313824

Reed SB, Riley W.
Eval Health Prof. 1979 Dec;2(4):438-54. doi: 10.1177/016327877900200403.
PMID: 10244879

Aamodt AM.
West J Nurs Res. 1983;5(4):398-402. doi: 10.1177/019394598300500422.
PMID: 6559494

Watling CJ, Lingard L.
Med Teach. 2012;34(10):850-61. doi: 10.3109/0142159X.2012.704439. Epub 2012 Aug 22.
PMID: 22913519

Morgan DL.
Qual Health Res. 2015 Jun;25(6):789-93. doi: 10.1177/1049732315580110. Epub 2015 Apr 09.
PMID: 25857655

Hogan MD, Kupper LL.
Am J Epidemiol. 1978 Aug;108(2):159-60. doi: 10.1093/oxfordjournals.aje.a112603.
PMID: 707479

[No authors listed]
Bull World Health Organ. 1951;3(3):402-8.
PMID: 20603945