I think we can agree that 'l' is the common symbol in Europe, whereas 'L' is used in the USA. Here are some sources of further information for those interested.
ISO 31-0:1992(E) "The two symbols for litre are on an equal footing. The CIPM will, however, make a survey on the development of the use of the two symbols in order to see if one of the two may be suppressed." Selected parts from: Bureau Internationaldes Poids et Mesures, The International System of Units (SI), 7th edition, 1998 (available online at http://www.bipm.fr/enus/6_Publications/si/si-brochure.html) "(c) This unit and the symbol l were adopted by CIPM in 1879 (PV, 1879, 41). The alternative symbol , L , was adopted by the 16th CGPM (1979, Resolution 6; CR, 101 and Metrologia, 1980, 16, 56-57) in order to avoid the risk of confusion between the letter l and the number 1. The present definition of the litre is given in Resolution 6 of the 12th CGPM (1964; CR, 93)." (p. 105) "The 16th Conf�rence G�n�rale des Poids et Mesures (CGPM), recognizing the general principles adopted for writing the unit symbols in Resolution 7 of the 9th CGPM (1948), considering that the symbol l for the unit litre was adopted by the Comit� International des Poids et Mesures (CIPM) in 1879 and confirmed in the same Resolution of 1948, considering also that, in order to avoid the risk of confusion between the letter l and the number 1, several countries have adopted the symbol L instead of l for the unit litre, considering that the name litre, although not included in the Syst�me International d'Unit�s, must be admitted for general use with the System, decides, as an exception, to adopt the two symbols l and L as symbols to be used for the unit litre, considering further that in the future only one of these two symbols should be retained, invites the CIPM to follow the development of the use of these two symbols and to give the 18th CGPM its opinion as to the possibility of suppressing one of them." (p. 131f) "The CIPM, in 1990, considered that it was still too early to choose a single symbol for the litre." (p. 132) So, the unit litre is in fact the only one with two officialy accepted symbols. So, besides any local practice, one has to consider which symbol - if any - is preferrable and should be supported. Eckhart
