If you study design, you need a fundamental knowledge of theory, and design theory must also have an empirical relation to the real needs of real people. Therefore, this book is an introduction to both design research and design theory. Expertly written, this easy-to-read book provides information on qualitative and quantitative methods in design research. It also offers a theory toolset, describes the prospects of design research and much more.

Uta Brandes, Michael Erlhoff & Nadine Schemman (2009)
Designtheorie und Designforschung
UTB/W. Fink
German
http://bit.ly/2GyjWDI