I. Helfrich

A multinational survey of prevalence and patterns of laxative use among adults with self‐defined constipation

M. Kamm, C. Scarpignato, A. Wald, 2008, Alimentary pharmacology & therapeutics.

The burden of constipation on quality of life: results of a multinational survey

M. Kamm, O. Petrini, C. Scarpignato, 2007, Alimentary pharmacology & therapeutics.

Prevalence and management of abdominal cramping and pain: a multinational survey

G. Locke, E. Quigley, G. Tytgat, 2006, Alimentary pharmacology & therapeutics.

Drug treatment of chronic‐intermittent abdominal cramping and pain: a multi‐national survey on usage and attitudes

E. Quigley, S. Mueller-Lissner, I. Helfrich, 2010, Alimentary pharmacology & therapeutics.