Correction of Parnas reference from 1978 to 1975

Lectures/L02_SoftEngProfession/SoftEngProfession.tex

@@ -125,7 +125,7 @@ TBD
 \end{itemize}
 \item ``Application of a systematic, disciplined, quantifiable approach to the development,
 operation and maintenance of software'' (IEEE 1990)
-\item ``Multi-person construction of multi-version software'' (Parnas 1978)
+\item ``Multi-person construction of multi-version software'' (Parnas 1975)
 \item Like other engineering areas, SE relies on mathematical techniques, especially
 logic and discrete mathematics
 \item Analogous to other engineering disciplines