Presence information of presentities is logged in a calendar system using a presence logging calendar connector. In an electronic document, signature blocks are used to embed the digital signatures. The use of different solvent liquids for the feedstream and the desorbent stream results in an increased difference in partition coefficients for solute A and solute B. When it is not possible to ensure a band necessary for transferring the VolP packet in the label switching path, a label switching path is established between the pair of edge label switch routers. The pupil expanding element may be disposed at a position which is offset from an intermediate image plane occurring between the light source and the light exit, along and within an optical path defined between the light source and the light exit.