Sheltran is 'structured Fortran' - this being ANSI Fortran 77 with certain facilities replaced by corresponding 'structured' facilities, plus additional facilities with no Fortran equivalents.
Sheltran declares statement labels (except for the FORMAT statement) illegal, and hence any control statement requiring statement labels as arguments is also illegal. These statements are replaced by closely-matching 'structured' facilities with controlled exits. Sheltran also provides various forms of the repetition construct (allowing controlled exits).
The Sheltran language and the translator were developed by G.A. Croes and F. Deckers in 1975. The translator was originally written to generate ANSI-66 FORTRAN. At the Kapteyn Institute it has later been rewritten and extended to generate Fortran-77.