[Tex/LaTex] How to align equations to the left side

Question

I'm using MiKTeX 2.9 on Windows 7 with Texmaker
and I'm trying to left align some equations like these:

\usepackage{amsmath}
\begin{flalign}
 a)   I_g : N_{log} \rightarrow M\left(p, p, \phi \right) \mbox{is
compact.} \nonumber \\
 b)   I_g : N_{log}^0 \rightarrow M\left(p, p, \phi \right) \mbox{is
compact.} \nonumber \\
 c)   \int \limits _ {\mathbb{D}}   \frac{\left(g
\left(z\right)\right)^p}{log \left( \frac{2}{1- \mid z \mid
^2}\right)^p}   \frac{\phi^p \left(|z|\right)}{1- \mid z \mid } d
A(z) < \infty .
\end{flalign}

I get the message:

Package amsmath Error: Erroneous nesting of equation structures;
(amsmath)                trying to recover with `aligned'.

Answer 1

I see this an abuse of flalign: your readers will have a hard time at guessing whether the number refers to all three conditions or just to the integral.

You could use aligned, so the number would be vertically centered:

\documentclass{article}
\usepackage{amsmath,amssymb}
\usepackage{lipsum} % just for the example

\begin{document}

\lipsum*[2]% stands for text before the display
\begin{flalign}
&\begin{aligned}
\text{a)}&\quad I_g \colon N_{\log} \rightarrow M(p, p, \phi) \text{ is compact.} \\
\text{b)}&\quad I_g \colon N_{\log}^0 \rightarrow M(p, p, \phi) \text{ is compact.} \\
\text{c)}&\quad \int\limits_{\mathbb{D}}
                \frac{(g(z))^p}{\log\bigl(\frac{2}{1-\lvert z\rvert^2}\bigr)^p}
                \frac{\phi^p (\lvert z\rvert)}{1-\lvert z\rvert}\,dA(z) < \infty.
\end{aligned}&&
\end{flalign}
\lipsum[3]

\end{document}

You might consider the following subequations approach:

\documentclass{article}
\usepackage{amsmath,amssymb}
\usepackage{lipsum} % just for the example

\begin{document}

\lipsum*[2]% stands for text before the display
\begin{subequations}\label{global}
\begin{align}
\label{particular-a}
& I_g \colon N_{\log} \rightarrow M(p, p, \phi) \text{ is compact.} \\
\label{particular-b}
& I_g \colon N_{\log}^0 \rightarrow M(p, p, \phi) \text{ is compact.} \\
\label{particular-c}
& \int\limits_{\mathbb{D}}
    \frac{(g(z))^p}{\log\bigl(\frac{2}{1-\lvert z\rvert^2}\bigr)^p}
    \frac{\phi^p (\lvert z\rvert)}{1-\lvert z\rvert}\,dA(z) < \infty.
\end{align}
\end{subequations}
\lipsum[3]

\end{document}

You can use \eqref{global} for referring to the common number, but also \eqref{particular-c} for referring to the third condition.