Usually one begins by adding up the individual spectra obtained at a single position on the sky. To do this, define the Selection Criteria of the spectra, including the Line Name (3), the Source Name (4), the Telescope and backend configuration used (5), and the date of observations (6). In this example we consider all the observations of the 13CO(1-0) transition performed using the IRAM 30-m telescope in the direction of IC348 on 1984 August 15th. Commands (7) and (8) further define the angular coordinate system to be used, and the corresponding units. Executing the FIND command (9) builds up an Index of these observations, where the selection criteria defined by the previous SET commands are further extended by the /OFFSET option which limits the search to the position (0.,25.) (in equatorial coordinates and arc seconds, as defined by (7) and (8)). The SUM command then adds up all the spectra of the current index.