/usr/include/ql/math/copulas/ is in libquantlib0-dev 1.7.1-1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/ql/math/copulas/alimikhailhaqcopula.hpp
/usr/include/ql/math/copulas/all.hpp
/usr/include/ql/math/copulas/claytoncopula.hpp
/usr/include/ql/math/copulas/farliegumbelmorgensterncopula.hpp
/usr/include/ql/math/copulas/frankcopula.hpp
/usr/include/ql/math/copulas/galamboscopula.hpp
/usr/include/ql/math/copulas/gaussiancopula.hpp
/usr/include/ql/math/copulas/gumbelcopula.hpp
/usr/include/ql/math/copulas/huslerreisscopula.hpp
/usr/include/ql/math/copulas/independentcopula.hpp
/usr/include/ql/math/copulas/marshallolkincopula.hpp
/usr/include/ql/math/copulas/maxcopula.hpp
/usr/include/ql/math/copulas/mincopula.hpp
/usr/include/ql/math/copulas/plackettcopula.hpp