Title favourites Novak Djokovic and Serena Williams have reached the third round of the Singles event at the Australian Open Tennis championships, alongside China's Li Na.In the Men's Singles, Djokovic comfortably beat Argentina's Leonardo Mayer 6-0, 6-4, 6-4, extending his Melbourne streak to 23 straight wins. In the Women's Singles, world number one and top seed Serena Williams crushed Serbia's Vesna Dolonc 6-1, 6-2 in just 63 minutes. Williams is aiming for her 18th Grand Slam title, a tally which would match Chris Evert and Martina Navratilova. Another serious title contender, Li Na, subdued 16-year old Swiss teenager Belinda Bencic in straight sets 6-0, 7-6. Among the other Men's Singles winners today were Spanish third seed David Ferrer, eighth seed Stanislas Wawrinka, French ninth seed Richard Gasquet, Tomas Berdych and big-serving Polish 20th seed Jerzy Janowicz.In the women's section, Serbia's Ana Ivanovic thrashed Annika Beck 6-1, 6-2. Other players through included Russian 22nd seed Ekaterina Makarova, Italian Flavia Pennetta and Germany's Mona Barthel, who swept past Thai hope Luksika Kumkhum.Defending champion Victoria Azarenka, gunning for her third straight Australian Open title, and third seed Maria Sharapova play their second round matches on Thursday.