Erratum to: Long-term monitoring of opioid, sedative and anti-inflammatory drugs in horse hair using a selective and sensitive LC-MS/MS procedure. Issue 1 (December 2016) - Madry, Milena; Spycher, Barbara; Kupper, Jacqueline; Fuerst, Anton; Baumgartner, Markus; Kraemer, Thomas; Naegeli, Hanspeter