SLICSel uses mfold (version 3.2) by Zuker and Turner to calculate oligonucleotide secondary structures.

M. Zuker
Mfold web server for nucleic acid folding and hybridization prediction.
Nucleic Acids Res. 31 (13), 3406-15, (2003)
[Abstract] [Full Text] [Supplementary Material] [Additional Information]