Model is underconstrained.
The following variables couldn't be defined:
 * DR in component DR
 * d/dt R in component R
 * d/dt D in component R
 * d/dt DR in component DR
 * d/dt DRG_GDP in component DRG_GDP
 * d/dt DRG in component DRG
 * d/dt DRG_GTP in component DRG_GTP
 * d/dt Gstar_GTP in component Gstar_GTP
 * d/dt G_GDP in component G_GDP