Safety Is not a Restriction at Level 2 for String Languages. - Klaus Aehlig; Jolie G. de Miranda; C.-H. Luke Ong (FoSSaCS, 2005)

The Monadic Second Order Theory of Trees Given by Arbitrary Level-Two Recursion Schemes Is Decidable. - Klaus Aehlig; Jolie G. de Miranda; C.-H. Luke Ong (TLCA, 2005)

Structures generated by higher-order grammars and the safety constraint. - Jolie G. de Miranda (2006)