Definition mequiv P Q := P ⪯ Q /\ Q ⪯ P.
Notation "P ≡𝐦 Q" := (mequiv P Q) (at level 40).
Instance Subrel_mequiv : subrelation mequiv mreducible.
Instance mequiv_proper : Proper (mequiv ==> mequiv ==> iff) mreducible.
Instance Equivalence_mequiv : Equivalence mequiv.

(* Specifications: *)
Lemma m_complete_red P Q :
m_complete P -> m_complete Q -> P ≡𝐦 Q.
Lemma m_complete_K : m_complete eva.
Lemma mcomplete_creative P : m_complete P -> creative P.
Lemma simple_dec P : simple P -> ~ decidable P.
Lemma simple_creative P : simple P -> ~ creative P.
Lemma simple_nontrivial P : simple P -> exists s t, P s /\ ~ P t.
Admitted.
Lemma simple_between P :
simple P -> 𝐎𝐦 <𝐦 mdegree_of P /\ mdegree_of P <𝐦 𝐎𝐦'.