Add link to goto program documentation from central data structures

Author: thomasspriggs

doc/architectural/central-data-structures.md

@@ -108,7 +108,10 @@ in the symbol-table for their definitions.
 ## goto_programt
 
 A  goto program  is a sequence of GOTO instructions (`goto_instructiont`). For
-details see the documentation of the `goto_programt` class.
+details of the `goto_programt` class itself see the documentation in
+[`goto_program.h`](../../src/goto-programs/goto_program.h). For further details
+of the life cycle of goto programs see
+[`src/goto-programs/README.md`](../../src/goto-programs/README.md).
 
 An instruction (`goto_instructiont`) is a triple (an element with three subcomponents),
 describing a GOTO level instruction with the following 3 component subtypes,