“…There have been intensive experimental searches for axions, see [46,66,75] and references therein. Constraints on the axion mass and coupling to the electromagnetic field have been obtained both from astrophysical observations as from laboratory experiments, see [46,66,75] for details. Constraints on the axion mass and coupling to the electromagnetic field have been obtained both from astrophysical observations as from laboratory experiments, see [46,66,75] for details.…”