A cost efficient spatially balanced hierarchical sampling design for monitoring boreal birds incorporating access costs and habitat stratification. oleh Steven L Van Wilgenburg, C Lisa Mahon, Greg Campbell, Logan McLeod, Margaret Campbell, Dean Evans, Wendy Easton, Charles M Francis, Samuel Haché, Craig S Machtans, Caitlin Mader, Rhiannon F Pankratz, Rich Russell, Adam C Smith, Peter Thomas, Judith D Toms, Junior A Tremblay