diff --git a/symptom_ex_process/algorithm.tex b/symptom_ex_process/algorithm.tex
index 3dc399b..4846e9c 100644
--- a/symptom_ex_process/algorithm.tex
+++ b/symptom_ex_process/algorithm.tex
@@ -165,12 +165,12 @@ $$ DTC(F) = TC $$
    \ENDIF
 
    \IF{Double fault checking} 
-   \STATE { let $f1,f2$ represet a component failure modes }
+   \STATE { let $f1,f2$ represet a component failure modes, and $c$ a component in the functional group }
    %\ENSURE { That all failure modes are represented in at least one test case }
-   \ENSURE { $ \forall f1,f2 \;where\; \not(f1,f2) \in c\;such\;that\; (f \in F))    \wedge  (f \in \bigcup TC) $ }
-   \COMMENT { This corresponds to checking that at least each possible double failure mode is considered at 
-              least once in the analysis; more rigorous cardinality constraint
-              checks may be required for some safety standards. Not if both failure modes
+   \ENSURE { $ \forall f1,f2 \;where\; (f1,f2) \not\in c\;such\;that\; (f \in F))    \wedge  (f \in \bigcup TC) $ }
+   \COMMENT { This corresponds to checking that each possible double failure mode is considered  
+              as a test case; more rigorous cardinality constraint
+              checks may be required for some safety standards. Note if both failure modes
               in the check are sourced from the same component $c$ the test case is impossible
               under unitary state failure mode conditions}
    \ENDIF
@@ -312,6 +312,7 @@ $$ CDC:  \mathcal{SP} \mapsto \mathcal{DC} $$
      \STATE { $DC := DC \cap f_l$ } \COMMENT{ this is saying place $f_l$ into $DC$'s collection of failure modes}
 
    \ENDFOR 
+   \ENSURE { $FM(DC) \neq \emptyset$ } \COMMENT{Ensure that DC has a known set of failure modes}
   \RETURN DC
 %\hline
 
@@ -322,7 +323,7 @@ Algorithm \ref{alg:sympabs55} is the final stage in the process. We now have a
 derived~component $DC$, which has its own set of failure~modes. This can now be
 used in with other components (or derived~components) 
 to form functional~groups at higher levels of failure~mode~abstraction.
-Hierarchies of fault abstraction can be built that can model an entire SYSTEM.
+%Hierarchies of fault abstraction can be built that can model an entire SYSTEM.
 
 \section{Linking all five stages}
 
@@ -334,10 +335,10 @@ $$ \bowtie: \mathcal{FG} \mapsto \mathcal{DC} $$
 
 \begin{algorithmic}[1]
 
-   \STATE {F  = FM (FG)}  \COMMENT{ collect all the failure modes from the from the components in the functional~group  }
-   \STATE {TC  = DTC (F)}  \COMMENT{ determine all test cases to apply to the functional group }
-   \STATE {R  = ATC (TC)}  \COMMENT{ analyse the test cases, for failure mode behaviour of the functional~group }
-   \STATE {SP  = FCS (R)}  \COMMENT{ find common symptoms of failure for the functional group  }
+   \STATE {F  = FM (FG)}  \COMMENT{ collect all component failure modes }%from the from the components in the functional~group  }
+   \STATE {TC  = DTC (F)}  \COMMENT{ determine all test cases } %to apply to the functional group }
+   \STATE {R  = ATC (TC)}  \COMMENT{ analyse the test cases }%, for failure mode behaviour of the functional~group }
+   \STATE {SP  = FCS (R)}  \COMMENT{ find common symptoms }%of failure for the functional group  }
    \STATE {DC  = CDC (SP)}  \COMMENT{ create a derived component }
 
  \RETURN $DC$