The geometry of contact Lee forms and a contact analog of Ikuta’s theorem

Questions of the conformal geometry of quasi-Sasakian manifolds are studied. A contact analog of Ikuta’s theorem is obtained. It is proved that a regular locally conformally quasi-Sasakian structure is normal if and only if it is locally conformally cosymplectic and has closed contact form. It is shown that the Kenmotsu structures have these properties and that a structure with the above properties is a Kenmotsu structure if and only if its contact Lee form coincides with the contact form.