@book{ ROSALES_GARCÍA,

author = { JOSE CARLOS ROSALES GONZALEZ and PEDRO ABELARDO GARCÍA SÁNCHEZ } ,

title = { NUMERICAL SEMIGROUPS },

publisher = { Springer },

address = { NUEVA YOURS, ESTADOS UNIDOS },

year = { 2009 },

isbn = { 978-1-4419-0159-0 },

}