The terms "Estoppel in pais" and equitable estoppel are used interchangeably in American law. The principle is called collateral estoppel or issue preclusion. Laches is a form of "estoppel" for delay. The remedy for promissory estoppel is reliance damages. The doctrine of promissory estoppel may not make the total contract fully enforceable. Modern contract theory has also permitted remedies on alternative theories such as promissory estoppel. The wife brought an action to enforce the promise invoking promissory estoppel. The federal approach has been described as merging principles of equitable tolling and equitable estoppel. Promissory estoppel or unjust enrichment may be available, but generally are not. Additionally, unconscionability is a necessary element to the finding of proprietary estoppel. The doctrine of promissory estoppel was adopted into Australian law in "Legione v Hateley". A fourth category, equitable easements arising by virtue of proprietary estoppel, is contested. In English law, proprietary estoppel is distinct from promissory estoppel. In English law, "proprietary estoppel" is distinct from promissory estoppel.