1 Laser diagnostics and minor species detection in combustion using resonant four-wave mixing: a review Johannes Kiefer 1,2 and Paul Ewart 3 1 School of Engineering, University of Aberdeen, Aberdeen, UK 2 Erlangen Graduate School in Advanced Optical Technologies (SAOT), University Erlangen- Nuremberg, Erlangen, Germany 3 Department of Physics, Clarendon Laboratory, University of Oxford, Oxford, UK Corresponding author: Johannes Kiefer School of Engineering University of Aberdeen Fraser Noble Building Aberdeen AB24 3UE United Kingdom Tel: +44 1224 272495 Email: j.kiefer@abdn.ac.uk