Figure 3.

Schematic displaying the identifiability conditions for the MTD model (top) and the mLTD model (bottom) for an example with $d=3$ and $m_1=m_2=m_3=3$. Identifiability for MTD requires a zero entry in each row of ${\mathbf{Z}}^j$, while for mLTD the first column and last row must all be zero. In MTD the columns of each ${\mathbf{Z}}^j$ must also sum to the same value, and must sum to one across all ${\mathbf{Z}}^j$.