Carson–Long-style left-libertarianism is rooted in 19th-century mutualism and in the work of figures such as Thomas Hodgskin, French Liberal School thinkers such as Gustave de Molinari and American individualist anarchists like Benjamin Tucker and Lysander Spooner, among others. Certain American left-wing market anarchists who come from the left-Rothbardian school such as Roderick T. Long and Sheldon Richman cite Murray Rothbard's homestead principle with approval to support worker cooperatives. While American market-oriented left-libertarians after Benjamin Tucker tended to ally with the political right (with notable exceptions), relationships between such libertarians and the New Left thrived in the 1960s, laying the groundwork for modern free-market left-libertarianism.