Algebraic quantum groupoids have been developed by two of the authors of this note (AVD and SHW) in a series of papers [34, 35, 36] and [37], see also [32]. By an algebraic quantum groupoid, we understand a regular weak multiplier Hopf algebra with enough integrals. Regular multiplier Hopf algebroids are obtained also by two authors of this note (TT and AVD) in [20]. Integral theory and duality for those have been studied by one author here (TT) in [18,19]. In these papers, the term algebraic quantum groupoid is used for a regular multiplier Hopf algebroid with a single faithful integral. Finally, again two authors of us (TT and AVD) have investigated the relation between weak multiplier Hopf algebras and multiplier Hopf algebroids in [21].(2) Address: