References Flat module

bican, l.; el bashir, r.; enochs, e. (2001), modules have flat covers , bull. london math. soc., 33 (4): 385–390, doi:10.1017/s0024609301008104, issn 0024-6093, mr 1832549 
n. bourbaki, commutative algebra
eisenbud, david (1995), commutative algebra, graduate texts in mathematics, 150, berlin, new york: springer-verlag, isbn 978-0-387-94268-1, mr 1322960, isbn 978-0-387-94269-8 
enochs, edgar e. (1981), injective , flat covers, envelopes , resolvents , israel j. math., 39 (3): 189–209, doi:10.1007/bf02760849, issn 0021-2172, mr 0636889 
enochs, edgar e.; jenda, overtoun m. g. (2000), relative homological algebra, de gruyter expositions in mathematics, 30, berlin: walter de gruyter & co., isbn 978-3-11-016633-0, mr 1753146 
lam, tsit-yuen (1999), lectures on modules , rings, graduate texts in mathematics no. 189, berlin, new york: springer-verlag, isbn 978-0-387-98428-5, mr 1653294 
mac lane, saunders (1963), homology, die grundlehren der mathematischen wissenschaften, bd. 114, boston, ma: academic press, mr 0156879 
matsumura, hideyuki (1970), commutative algebra 
mumford, david, red book of varieties , schemes 
northcott, d. g. (1984), multilinear algebra, cambridge university press, isbn 978-0-521-26269-9  - page 33
richman, fred (1997), flat dimension, constructivity, , hilbert syzygy theorem , new zealand journal of mathematics, 26 (2): 263–273, issn 1171-6096, mr 1601663 
serre, jean-pierre (1956), géométrie algébrique et géométrie analytique , université de grenoble. annales de l institut fourier, 6: 1–42, doi:10.5802/aif.59, issn 0373-0956, mr 0082175