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**School starts soon, and I know students are looking to get their textbooks at bargain prices**

Inspired by this thread I thought that I could share some of my findings of

**100% legally free textbooks and lecture notes in mathematics and mathematical physics**(mostly focused on geometry) (some of these are pre-prints of published books) (some you can download as a pdf, some you have to read online)

**There are many many more out there, and I have for sure not read all of the ones in this post. If you have read any of these, or have other suggestions, feel free to share it in this thread**(The ones that I have read, I will write about at some point).

**Note:**I have

__not__included video lecture series, or interactive sites, only stuff you can read like a textbook.

I might do another thread in the future for physics books...

Anyway, here you go, enjoy

Differential equationsâNotes of Diffy Qs: Differential equations for engineersâhttps://www.jirka.org/diffyqs/diffyqs.pdf more info https://www.jirka.org/diffyqs/ Even though the title says âfor engineersâ the stuff should be pretty good for for pure math and physics too!âDifferential equations (Paulâs online notes)â https://tutorial.math.lamar.edu/Classes/DE/DE.aspx âElementary differential equationsâhttps://digitalcommons.trinity.edu/cgi/viewcontent.cgi?article=1007&context=mono âDifferential equations (Math online)â http://mathonline.wikidot.com/differential-equations "Ordinary Differential Equations and Dynamical Systems (Teschl)"https://www.mat.univie.ac.at/~gerald/ftp/book-ode/ode.pdf more info https://www.mat.univie.ac.at/~gerald/ftp/book-ode/ |

Complex analysisâA first course in complex analysisâ http://math.sfsu.edu/beck/papers/complexorth.pdf more info https://matthbeck.github.io/complex.html âGuide to Cultivating Complex Analysis - Working the Complex Fieldâhttps://www.jirka.org/ca/ca.pdf more info https://www.jirka.org/ca/ âComplex analysisâhttp://mathonline.wikidot.com/complex-analysis |

Abstract algebraâAbstract algebra: Theory and applicationsâhttp://abstract.ups.edu/download/aata-20220728.pdf more info http://abstract.ups.edu/ âAlgebra: abstract and concreteâhttp://homepage.divms.uiowa.edu/~goodman/algebrabook.dir/book.2.6.pdf more info http://homepage.divms.uiowa.edu/~goodman/algebrabook.dir/algebrabook.html âElements of abstract and linear algebraâhttps://www.math.miami.edu/~ec/book/book.pdf more info https://www.math.miami.edu/~ec/book/ âAbstract algebraâhttp://mathonline.wikidot.com/abstract-algebra âIntroduction to algebraic structuresâhttps://batch.libretexts.org/print/Finished/math-666/Full.pdf more info https://math.libretexts.org/Bookshelves/Abstract_and_Geometric_Algebra/Introduction_to_Algebraic_Structures âAbstract algebra: the basic graduate yearâhttps://faculty.math.illinois.edu/~r-ash/Algebra.html |

TopologyâTopology without tearsâ http://www.topologywithouttears.net/topbook.pdf more info https://www.topologywithouttears.net/ âTopologyâhttp://mathonline.wikidot.com/topology |

Measure theory and integrationâMeasure, Integration & Real Analysisâ https://measure.axler.net/MIRA.pdf more info https://measure.axler.net/ âAn introduction to measure theoryâhttps://terrytao.files.wordpress.com/2012/12/gsm-126-tao5-measure-book.pdf more info https://terrytao.wordpress.com/books/an-introduction-to-measure-theory/ âMeasure theoryâhttp://mathonline.wikidot.com/measure-theory |

Functional analysisâLectures on functional analysisâ http://facultymembers.sbu.ac.ir/shahrokhi/HasseOpeThe.pdf âIntroduction to functional analysis (Daners)âhttps://www.maths.usyd.edu.au/u/athomas/FunctionalAnalysis/daners-functional-analysis-2017.pdf âIntroduction to functional analysis (Kisil)âhttp://www1.maths.leeds.ac.uk/~kisilv/courses/math3263m.pdf âFunctional analysisâhttp://mathonline.wikidot.com/functional-analysis |

Differential geometry/ Mathematical PhysicsâDifferential geometry in physicsâhttp://people.uncw.edu/lugo/COURSES/DiffGeom/DG1.pdf more info http://people.uncw.edu/lugo/COURSES/DiffGeom/index.htm âQuick introduction to tensor analysisâhttps://arxiv.org/pdf/math/0403252.pdf âA geometrical approach to differential formsâhttps://maths.dur.ac.uk/users/mark.a.powell/Bachman_Geometric_Approach_to_Differential_Forms.pdf âA simple introduction to particle physics part IIâhttps://arxiv.org/pdf/0908.1395.pdf part I is also worth to check out âMathematics for Physics: An illustrated handbookâhttps://www.mathphysicsbook.com/intro/ |

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