@article { 1755,
	title = {Critical Lines and Massive Phases in Quantum Spin Ladders with Dimerization},
	volume = {77},
	year = {2008},
	pages = {094415},
	publisher = {Phys. Rev. B},
	address = {Phys. Rev. B },
	URL = {http://arxiv.org/abs/0707.4452},
	author = {Javier Almeida, M.A. Martin-Delgado, G. Sierra}
}