Summary
Marcin Bownik, Ole Christensen, Xinli Huang and Baiyun Yu (2012) Extension of shift-invariant systems in L^2(R) to frames. Numer. Funct. Anal. Optim., 33(7-9):833–846. 
Bibtex entry
@ARTICLE { MR2966134,
AUTHOR = { Marcin Bownik and Ole Christensen and Xinli Huang and Baiyun Yu },
TITLE = { Extension of shift-invariant systems in L^2(R) to frames },
JOURNAL = { Numer. Funct. Anal. Optim. },
FJOURNAL = { Numerical Functional Analysis and Optimization. An International Journal },
VOLUME = { 33 },
YEAR = { 2012 },
NUMBER = { 7-9 },
PAGES = { 833--846 },
ISSN = { 0163-0563 },
CODEN = { NFADOL },
MRCLASS = { 42C15 (42C40) },
MRNUMBER = { 2966134 },
MRREVIEWER = { J{\'e}r{\^o}me Gilles },
DOI = { 10.1080/01630563.2012.682131 },
URL = { http://dx.doi.org/10.1080/01630563.2012.682131 },
}