Not being a native English speaker, I could be wrong but,
to me,
P14.
1 Let N an empty node list.
I feel more comfortable with ..

1 Let N be an empty node list.

Ditto for  P20

1 Let n a node that has a value reference (@cdl:ref) to be resolved.
2 Let N the node list that contains nodes identified with the reference.
3 Let N' an empty node list.
=>
1 Let n be a node that has a value reference (@cdl:ref) to be resolved.
2 Let N be the node list that contains nodes identified with the reference.
3 Let N' be an empty node list.