[ BeginEnv "axiom"
, Label "cons"
, BeginEnv "math"
, Variable "x"
, Command "in"
, Command "cons"
, InvisibleBraceL
, Variable "y"
, InvisibleBraceR
, InvisibleBraceL
, Variable "X"
, InvisibleBraceR
, EndEnv "math"
, Word "iff"
, BeginEnv "math"
, Variable "x"
, Symbol "="
, Variable "y"
, EndEnv "math"
, Word "or"
, BeginEnv "math"
, Variable "x"
, Command "in"
, Variable "X"
, EndEnv "math"
, Symbol "."
, EndEnv "axiom"
, BeginEnv "definition"
, Label "unit"
, BeginEnv "math"
, Command "unit"
, Symbol "="
, VisibleBraceL
, Command "emptyset"
, VisibleBraceR
, EndEnv "math"
, Symbol "."
, EndEnv "definition"
, BeginEnv "proposition"
, Label "emptyset_in_unit"
, BeginEnv "math"
, Command "emptyset"
, Command "in"
, Command "unit"
, EndEnv "math"
, Symbol "."
, EndEnv "proposition"
]