Editing Open Problems (section)

==== Initial context assumption ====

As with many results that demonstrate CRNs capable of complex computation <ref name="SCWB2008" /><ref name="TC2012">Thachuk, C., & Condon, A. (2012). Space and energy efficient computation with DNA strand displacement systems. In DNA Computing and Molecular Programming (pp. 135-149). Springer Berlin Heidelberg.</ref>, the stack machine construction in <ref name="QSW2011" /> assumes that certain molecular species are present in exact initial quantities, in particular there is exactly one copy of each stack.