1. Evaluation of a clinical test Part I: assessment of reliability;Khan;Br J Obstet Gynaecol,2001
2. Health Measurement Scales: A Practical Guide to Their Development and Use;Streiner,1995
3. Measuring measuring errors;Healy;Stat Med,1989
4. Medical Statistics. A Commonsense Approach;Campbell,1999
5. The validity and reliability of real time ultrasound estimation of bladder volume in postnatal women;Chien;J Obstet Gynaecol,1996