Zinc for the common cold - Health News - NHS Choices, su nhs.uk, 2012 [last update]. URL consultato il 24 febbraio 2012 (archiviato dall'url originale il 19 febbraio 2013).
«In this review, there was a high level of heterogeneity between the studies that were pooled to determine the effect of zinc on the duration of cold symptoms. This may suggest that it was inappropriate to pool them. It certainly makes this particular finding less conclusive.»