_:b663515816 . _:b663515816 . _:b663515816 . _:b663515816 . _:b663515816 "a two-dimensional continuant fiat boundary (surface) is a self-connected fiat surface whose location is defined in relation to some material entity. (axiom label in BFO2 Reference: [033-001])"@en . _:b663515816 . _:b663515816 .