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  • Contributors RH, HC, IG, CH, ATM-S and ES surveyed the literature and produced the research summaries. RH was responsible for organisation, editing, revisions and submission of this document.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; internally peer reviewed.