Erratum to: A systematic review of the characteristics and validity of monitoring technologies to assess Parkinson's disease.

Erratum

Unfortunately, the PDF and the XML of the original version of this article [1] contained an error and the references in the reference list starting from the second reference [21] were wrongly numbered:

the second reference [21], Del Din et al. (2015), should be reference [22];

reference [22], Godfrey et al. (2015), should be [23];

reference [23], Esculier et al. (2012), should be [24];

reference [24], Clark et al. (2010), should be [25];

reference [25], Holmes et al. (2013), should be [26];

reference [26], Chien et al. (2006), should be [27];

reference [27], Menz et al. (2004), should be [28];

reference [28], Brach et al. (2010), should be [29];

and reference [29], Giuffrida et al. (2009), should be [30].

Please refer to the HTML of the original article [1] for the correct reference list: http://jneuroengrehab.biomedcentral.com/articles/10.1186/s12984-016-0136-7.