Brother has documentation for many of their printers here: http://www.brother-usa.com/support/#.Tt73V1Yb1G8
. Select the type of printer and then the model.
As far as I know, LC61 is the first part of the code for the cartridges that several Brother multi-functional ink jet printers use. So please add a comment with your printer's model number for additional help. Also include if the screen message is on your computer or the printer itself. Please give details of the problem as well (an error code, details of whether you were printing from a networked computer or a device directly connected to the printer or scanning a document, or just turned it on).
For example the MFC-490CW uses the LC61BK, LC61C, LC61M and LC61Y cartridges. The direct link to the manual for this printer is http://www.brother-usa.com/ModelDocuments/Consumer/Users%20Manual/UM_MFC_490CW_EN_1773.PDF