Stocks Models Click on a model link below to view or download the model. The models with a .ltx extension are formatted for traditional LINDO, .lng and .lg4 for LINGO and .xls for What'sBest!. DNRISK.lng DNRISKWB.xls FACTOR.ltx GENPRT.lng MARKOW.c MARKSCEN.ltx MARKWTZ.ltx PORTCARD.lng PORTCOST.xls PORTHEDG.lng PORTMTCH.lng PORTSCEN.xls PORTVAR.lng PRTSCEN.lng PORTAX.lng RISKFREE.ltx SEMIVARI.ltx TRANCOST.ltx