Prof. Dr. Agust Gudmundsson, Royal Holloway University of London

Sonja was my PhD student at the University of Bergen (Norway) and our collaboration has continued since. She has been working on various problems in structural geology, hydrogeology, geothermy, and volcanotectonics. In Bergen, she was regarded as an absolutely outstanding PhD student. She very quickly learned the main topics of fracture mechanics as applied to geology, as well as fluid transport in porous and fractured media. 
While in Göttingen Professor Philipp’s main research and teaching has been on geothermal reservoirs, both naturally fractured reservoirs and Enhanced Geothermal Systems (EGS). She built up a very strong group of students around her activities, including many PhD students. She is an excellent teacher, gives very good lectures, and I regard the work of her group as uniformly outstanding and particularly appreciate the combination of very detailed quantitative field work with excellent analytical and numerical modelling work. 
Sonja is an outstanding scientist in the fields of geothermy/structural geology/hydrogeology and related fields – in particular in the field of fractured reservoirs and fluid transport. 

Dr. John Reinecker, geoThermal Engineering GmbH

I’ve got to know Sonja since 2012 when working together in a R&D project on outcrop analogue studies in geothermal exploration (AuGE project, financed by the German Federal Ministry for the Environment, Nature Conservation, and Nuclear Safety).  During intensive discussions on the way of approach and the applicability of outcrop studies in geothermal exploration I experienced Sonja as a colleague with high analyst standards and pragmatic thinking. In critical discussions she has the quest to apply Occam’s razor to move the project forward. This quality and her profound knowledge made me hire her as a freelancer for working on questions concerning characterization of fractured reservoirs and fault zones, as well as on fracture modelling. We also join again as applicants for R&D projects focusing fractured reservoir characterization associated with fault zones in hydrothermal projects. Sonja Philipp appears to me as a very polite and pleasant person and I appreciate her very much as a trustworthy colleague. It is a pleasure to discuss with her and search for new approaches in geothermal exploration.

Dr. Ralf Ehrlich, Norconsult AS, Oslo

I worked together with Sonja at the University of Bergen. We were both working on different projects, but Sonja was always open to good discussions. Sonja is very enthusiastic about her field of expertise and has a clear logic. Her creativity has helped me to look for alternative solutions for some of my technical problems with good success. She has always a smile and is easy to work with. Sonja earns my highest recommendation and I would not hesitate to contact and consult Sonja for her professional expertise and nice personality.

Prof. Ing. Volker Goebel, Endlager-Fachplaner, Zürich

Die Zusammenarbeit mit Frau Dr. Philipp war und ist von grossem Erkenntnis-Zugewinn und Nutzen. – Wir schätzen ganz besonders Ihre objektive geologische Fachmannschaft – Sie leistet einerseits eine ehrliche Wissenschaft und andererseits eine verständliche Schreibe, die die Endlager-Projekte nicht zerredet, sondern qualitativ präzise fördert. Wir stützen uns vertrauensvoll auf die Ergebnisse dieser Zusammenarbeit und können Frau Prof.-Dr. Philipp als Fachfrau für geologische Fragestellungen gerne aufgrund ihrer ausgezeichneten fachlichen und menschlichen Qualitäten weiter-empfehlen.