David Lester Using PVS to Validate the Inverse Trigonometric Functions of an Exact Arithmetic. 259-273 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2991&spage=259 2003 conf/dagstuhl/2003ns Numerical Software with Result Verification db/conf/dagstuhl/ns2003.html#Lester03