feat(proposal): add NASA paper to key background sources

pub/proposal/proposal.tex

@@ -75,6 +75,16 @@
     & \textbf{Reason:} The investigation found that the QRH was too
         lengthy and the pilots' used their experience to prioritize
         essential actions outside the QRH to keep the aircraft in control. \\
+
+    \multirow{2}{*}{\parbox{8em}{Design Guidance for Emergency and Abnormal Checklists in Aviation~\cite{nasa}}}
+    & \textbf{Description:} Provides the challenges and
+      requirements for designing aviation checklists.
+      It also talks about the problems that are in 
+      checklist designing. \\
+    & \textbf{Reason:} This will guide for certain aspects to
+      look out for whilst testing checklists, such as if
+      certain actions require waiting, or if it could be
+      completed in a different order. \\
     \bottomrule
 \end{tabularx}